System and method for product identification

ABSTRACT

A system and method for identifying an object includes a plurality of object sensors, each object sensor configured and arranged to determine at least one parameter describing objects as they are relatively moved with respect to a sensing volume and having a known position and attitude with respect to the sensing volume. A location sensor is configured and arranged to produce position information relating to the relative movement. Outputs from the object and location sensors are passed to a processor and the parameters are associated with respective ones of the objects on the basis of the position information and on the basis of the known positions and attitudes of the sensors. For each object having associated parameters, the processor compares the parameters to known item parameters to assign item identification to the object.

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/047,532, filed Mar. 14, 2011, now allowed, which claimspriority and benefit under 35 U.S.C. §119(e) to U.S. Provisional PatentApplication No. 61/430,804 filed Jan. 7, 2011 and U.S. ProvisionalApplication No. 61/313,256, filed Mar. 12, 2010, each of which isincorporated by reference in its entirety herein.

TECHNICAL FIELD

The description herein relates generally to methods and systems foridentifying items and more particularly for identifying items passingthrough a sensing volume.

BACKGROUND

In a variety of environments, it may be useful to identify objects andto read coded information related to those objects. For example,point-of-sale (POS) systems make use of bar code readers to identifyproducts to be purchased. Likewise, shipping, logistics and mail sortingoperations may make use of automated identification systems. Dependingon the context, coded information may include, prices, destinations, orother information relating to the object on which the code is placed. Ingeneral, it is useful to reduce a number of errors or exceptions thatrequire human intervention in the operation.

SUMMARY

Described herein are implementations of various approaches to itemidentification and code reading.

An aspect of an embodiment includes a method including determining atleast one parameter describing objects as they are relatively moved withrespect to a sensing volume using a sensor having a known position andattitude with respect to the sensing volume, generating locationinformation relating to the relative moving, and passing the parametersand the position information to a processor, and associating theparameters with respective ones of the objects on the basis of theposition information and on the basis of the known positions andattitudes of the sensors, and for each object having associatedparameters, comparing the parameters to known item parameters to assignitem identification to the object.

An aspect of an embodiment includes a system including a plurality ofsensors, each sensor configured and arranged to determine at least oneparameter describing objects as they are relatively moved with respectto a sensing volume and having a known position and attitude withrespect to the sensing volume, a location sensor, configured andarranged to produce position information relating to the relativemovement, and a processor, configured to receive the parameters and toassociate them with respective ones of the objects on the basis of theposition information and on the basis of the known positions andattitudes of the sensors and to compare the parameters to known itemparameters to assign item identification to the object.

An aspect of an embodiment of the invention includes a system forasynchronously identifying an item within a sensing volume includes aplurality of object sensors, each object sensor configured and arrangedto determine at least one parameter describing objects as they arerelatively moved with respect to the sensing volume, and having a knownposition and attitude with respect to the sensing volume. The systemincludes a position sensor, configured and arranged to produce positioninformation relating to the relative movement, wherein the positioninformation does not comprise system clock information and a processor,configured and arranged to receive the parameters from the objectsensors and to associate the parameters with respective ones of theobjects on the basis of the position information and on the basis of theknown position and attitude of the object sensor that determined eachrespective parameter, without taking into account system clockinformation, and to, for each object having at least one associatedparameter, compare the at least one associated parameter to known itemparameters to assign an item identification to the object.

An aspect of an embodiment of the invention includes a method ofasynchronously identifying an item within a sensing volume that includesdetermining at least one parameter describing objects as they arerelatively moved with respect to the sensing volume, using a pluralityof object sensors, each having a known position and attitude withrespect to the sensing volume. The method includes producing positioninformation relating to the relative movement, wherein the positioninformation does not comprise system clock information, and associatingthe parameters with respective ones of the objects on the basis of theposition information and on the basis of the known position and attitudeof the object sensor that determined each respective parameter, withouttaking into account system clock information, and to, for each objecthaving at least one associated parameter, compare the at least oneassociated parameter to known item parameters to assign an itemidentification to the object.

An aspect of an embodiment includes a tangible machine readable mediumencoded with machine executable instructions for performing a method asdescribed herein or for controlling an apparatus or system as describedherein.

The above summary section is provided to introduce a selection ofconcepts in a simplified form that are further described below in thedetailed description section. The summary is not intended to identifykey features or essential features of the claimed subject matter, nor isit intended to be used to limit the scope of the claimed subject matter.Furthermore, the claimed subject matter is not limited toimplementations that solve any or all disadvantages noted in any part ofthis disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features will become better understood with regard tothe following description, pending claims and accompanying drawingswhere:

FIG. 1 schematically illustrates an embodiment of a system for itemidentification;

FIG. 2A is an oblique view of an embodiment of a system for itemidentification;

FIG. 2B is an oblique view of the system of FIG. 2A;

FIG. 3A is an oblique right side view of an embodiment of a system foritem identification;

FIG. 3B is a top plan view of an embodiment of a system for itemidentification;

FIG. 3C is a right elevation view of an embodiment of a system for itemidentification;

FIG. 4A is a left elevation view of an embodiment of a system for itemidentification;

FIG. 4B is an oblique left side view of an embodiment of a system foritem identification;

FIG. 5A is an oblique cutaway left side view of an embodiment of asystem for item identification;

FIG. 5B is a cutaway left elevation view of an embodiment of a systemfor item identification;

FIG. 6A is a cutaway left elevation view of an embodiment of a systemfor item identification;

FIG. 6B is an oblique cutaway top view of an embodiment of a system foritem identification;

FIG. 7A is an oblique cutaway left side view of an embodiment of asystem for item identification;

FIG. 7B is a cutaway left elevation view of an embodiment of a systemfor item identification;

FIGS. 8-12 are data flow diagrams illustrating data flow through anembodiment of a system for item identification and its subsystems;

FIG. 13 is a timing diagram illustrating output of certain sensors in anembodiment of a system for item identification;

FIG. 14 is a data flow diagram illustrating data flow through anembodiment of a subsystem of a system for item identification; and

FIG. 15 is a data flow diagram illustrating data flow through anembodiment of a subsystem of a system for item identification.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates an object identification system 25. Oneor more items 20 to be identified are placed on a transport system to becarried through a sensing volume 240. In the notional embodiment shownhere, the transport system is a conveyor belt 31. As a practical matter,the transport system may be made up of more than one conveyor belt toallow for additional control over item flow through the sensing volume.In an embodiment, as illustrated in FIG. 3A, three belts are used: anin-feed conveyor belt, onto which the items to be identified are loaded;a sensing volume conveyor belt, which moves the items through thesensing volume 240; and an out-feed conveyor belt, which takes itemsaway from the sensing volume 240 for further processing. In, forexample, a retail environment, “further processing” may include bagging,reverse logistics processing, and other processing that known to thosehaving skill in the art. In some embodiments, the transport systemincludes only the sensing volume conveyor belt. Other belts, such as thein-feed conveyor belt or the out-feed conveyor belt can be addeddepending on the specific application contemplated.

As illustrated in the schematic diagram of FIG. 1, the transport systemmay be treated as if it were an infinite transport path. As will bedescribed in detail below, in an embodiment, the item identificationsystem may be designed in such a way that the processing algorithmstreat each segment of belt as if it were a unique location and any itemassociated with that segment is consistently treated as if it were atthat location. In this regard, the item identification system 25 mayhave no information regarding how or when items are placed on the beltand no information regarding what happens to them after they leave thesensing volume 240. In an embodiment, system 25 may assign linearlyincreasing location values to each segment of the essentially, endlessconveyor belt 31 as it enters sensing volume 240, analogous to a streetaddress, and the system may act as though the street has an unboundedlength. An item associated with a particular street address may beassumed to remain there.

Alternately, instead of moving objects through a fixed sensing volume,the volume could be scanned along fixed locations. That is, rather thana conveyor belt 31 moving objects, the sensing volume could be drivingdown the street looking at the items distributed at the ever increasingstreet address. For example, this could be applied in a warehouseenvironment in which a sensing device is driven along aisles and sensesitems arrayed on shelves.

The conveyor belt 31 is equipped with a transport location physicalsensor 122. Transport location physical sensor 122 measures the positionof the conveyor belt 31 relative to a fixed reference location in thesensing volume of the system 25. In some embodiments the transportlocation physical sensor 122 is an encoder associated with a roller ofthe sensing volume conveyor belt. The transport location physical sensor122 produces a pulse every time the essentially endless conveyor belt 31moves by a fixed incremental distance relative to the sensing volume240.

By way of example, a rotary encoder may include delineationscorresponding to 1 mil incremental movements of the conveyor belt 31. Inprinciple, each delineation produces a single count in anever-increasing accumulation, but in an embodiment, a number of countsmay be aggregated for each system count. As an example, each systemcount may correspond to five nominal detector counts. Additionally, itmay be useful to be able to account for slippage or other events thatcan cause a reverse movement of the belt. In this regard, one suchapproach would employ a quadrature encoder in which a pair of encoderoutputs are out of phase with each other by 90°. In this approach, adirection may be assigned to the belt motion on the basis of adetermination as to which of the two outputs occurred first.

The sensing volume 240 is the volume of space through which thetransport system carries the items 20, and is delineated by the combinedsensing regions/fields-of-view of a number of item parameter sensors220, including, but not limited to, the item isolator 140.

Sensing volume 240 includes a number of parameter sensors 220 forsensing items 20 traveling through it. Some embodiments have at leasttwo different parameter sensors 220: an item isolator and an indiciareading system which includes one or more indicia sensors. Inembodiments, additional parameter sensors, such as a dimension sensorand/or a weight sensor may be included. Parameter sensors may beunderstood as being the physical sensors, which convert some observableparameter into electrical signals, or the physical sensor in combinationwith an associated parameter processing function, which transforms rawdata (initial sensing data) into digital values used in furtherprocessing. The parameter processors can be co-located and/or embeddedwith the physical sensors or can be software modules running in parallelwith other modules on one or more general purpose computers.

In an embodiment, the output values measured by parameter sensors 220are transferred to other software modules in the processors. Thistransfer may be, in an embodiment, asynchronous. Data from the parametersensors 220 are associated with location information provided by thetransport system location sensor and sent to two processing modules: theitem description compiler 200, which performs the process of matchingall parameter values collected for a particular item to create an itemdescription, and the item identification processor 300, which queries aproduct description database to try to find a match between the itemdescription and a product, and outputs either a product identificationor an exception flag. Optionally, the system 25 may include an exceptionhandler (shown in FIG. 15).

An embodiment of an item identification system 25 is illustrated in FIG.2A. As shown, a sensing volume is within an upper housing 28. A lowerhousing 26 acts as a structural base for support of the sensing volumeconveyor belt (as shown in FIG. 3A), the transport location physicalsensor 122, and many of the optical and mechanical components of thesystem 25, including without limitation an upward looking line-scancamera 88. As will be appreciated, a line-scan camera has asubstantially planar field of view, though it is not strictly planar inthe mathematical sense, but rather is essentially a thin rectanglehaving a low divergence.

In embodiments, the sensing volume 240 may be partially enclosed suchthat the enclosing walls form a tunnel structure. As illustrated in FIG.2A, a tunnel structure is formed by the upper housing 28, providingconvenient locations onto which elements of the various sensors may beattached, as well as reducing the possibility of undesirable intrusionsinto the sensing volume 240 by miscellaneous hands and objects. In theembodiment shown in FIG. 2A, the upper housing 28 is used as astructural base for support of the laser stripe generator 119, the areacamera 152, the first area camera mirror 48, the second area cameramirror 49, illumination sources 40, the load cells 175, a light curtaingenerator 12, and various other optical and mechanical components.

The area camera 152 is aimed to observe the path of a line of laserlight, a laser stripe, projected downward towards the transport systemand any items thereon in its field of view. There is a known anglebetween the laser stripe generator 119 and the area camera 152 whichcauses the image of the laser stripe in the field of view of the areacamera 152 to be displaced perpendicular to the laser stripe inproportion to the height of the item on which the laser stripe isprojected.

As illustrated in FIG. 2B, a first load cell 175A, a second load cell(not seen from this perspective), a third load cell 175C and a fourthload cell (not seen from this perspective) are positioned to measure aload on the belt. Six line-scan cameras, including but not limited to alower right out-feed end line-scan camera 80 and an upward lookingline-scan camera 88, are shown mounted on the lower housing 26 in FIG.2B. In an embodiment, the system 25 includes eleven line-scan camerasarranged at various positions and various attitudes to fully cover thesensing volume within the upper housing. In an embodiment, each camerahas a position and attitude that are sufficiently well-known that alocation of a detected item can be determined to within less than about¼ in. (i.e., less than about 1 degree of arc). In this regard, thecameras may be precision mounted within a structural module such thatmounting the structural module to a frame member of the system providesprecise information regarding the direction in which the camera ispointed. In an embodiment, some or all of the cameras may include apolarizing filter to reduce specular reflection from packaging materialsthat can tend to obscure bar codes. In this configuration, it may beuseful to increase light output from the light sources in order tocompensate for light loss due to the polarizing filters.

The line-scan cameras are structured and arranged such that they have afield of view that includes line-scan camera mirrors. A first lowerright out-feed end line-scan mirror 92 is shown in FIG. 2B, as anexample of a line-scan mirror. The first lower right out-feed endline-scan mirror 92 reflects light from other line-scan mirrors (shownin FIG. 3A) into the lower right out-feed end line-scan camera 80, sothat the lower right out-feed end line-scan camera 80 produces line-scandata about the item when it arrives within its field of view on thesensing volume conveyor belt 32 (not visible in FIG. 2B, see FIG. 3A).Also shown in FIG. 2B is a right-side downward looking illuminationsource 128.

In an embodiment, the conveyor belt may be about 20 inches wide andtravel at a speed of about eighty feet per minute, or about sixteeninches per second. As will be appreciated, the speed of travel may beselected in accordance with the further processing operations to beperformed on items after identification. For example, a groceryapplication may require a relatively slow belt speed to allow for aclerk to perform bagging tasks while a package sorting application mayallow for a higher belt speed as sorted packages may be mechanicallyhandled.

As illustrated in FIG. 2B, the upper housing may be used as a structuralbase for support of the area camera 152, the first area camera mirror48, the second area camera mirror 49, illumination sources 40, andvarious of the optical and mechanical components of the system 25.

FIG. 3A illustrates right side camera optics usable to create images ofa first item 20A and a second item 20B. The first item 20A is shownhaving a front side 21, a top side 22 and a left side 23. While notshown in FIG. 3A, the first item 20A also has a bottom side, a back sideand a right side. While illustrated as a grocery product box in theFigures, the first item 20A could take the form of any item suitable forpassage through the sensing volume in accordance with a selectedapplication.

In the illustrated embodiment, first item 20A and the second item 20Bare transported into the sensing volume by an in-feed conveyor belt 30in the direction of motion toward the exit end of the in-feed conveyorbelt 30 and toward the in-feed end of the sensing volume conveyor belt32. The first item 20A and the second item 20B are transported throughthe sensing volume by sensing volume conveyor belt 32 in the directionof motion toward the exit end of the sensing volume conveyor belt 32 andtoward the in-feed end of the out-feed conveyor belt 34.

Upon entering the sensing volume, objects to be identified pass througha light curtain 10 generated by light curtain generator 12 as best seenin FIG. 4B. In the illustrated embodiment, the light curtain 10 isprojected down towards a gap 36 between the sensing volume conveyor belt32 and the in-feed conveyor belt 30 and is reflected by a mirror 14 to adetector 16. The light curtain generator may be, for example, a barincluding a linear array of LEDs, arranged to provide a substantiallyplanar sheet of light. The light curtain detector 16 may include alinear array of photodetectors that detect the light curtain projectedby the LEDs. In order to improve the spatial resolution and reduce falsenegative readings at the photodetectors, the LEDs and detectors aresequentially activated in pairs. This approach tends to reduce theeffects of potential stray light from one LED entering the detectorsdespite the presence of an object in the viewing field.

When an object passes through the curtain, it casts a shadow on thephotodetectors, providing information on a width of the object passingthrough the light curtain. A series of measurements of this type can beused as one set of parameters for identifying the object. In anembodiment, the spatial resolution of the light curtaingenerator/detector set will be on the order of a few mm, though inprinciple, finer or coarser measurements may be useful, depending on theapplication. For the grocery application, a finer resolution may berequired in order to distinguish similar product packages.

As seen in FIG. 3A, illumination sources 40 illuminate the sensingvolume conveyor belt 32. A lower right out-feed end line-scan camera 80has a field of view focused on a first lower right out-feed endline-scan mirror 92. The first lower right out-feed end line-scan mirror92 reflects light from a second lower right out-feed end line-scanmirror 93, which reflects light from a third lower right out-feed endline-scan mirror 94. The third lower right out-feed end line-scan mirror94 reflects light from the sensing volume conveyor belt 32. Thus, thelower right out-feed end line-scan camera 80 focuses its field of viewon the sensing volume conveyor belt 32, capturing line-scan data aboutthe first item 20A and the second item 20B as it is transported in thedirection of motion along the sensing volume conveyor belt 32. Alsoshown is upper right in-feed end line-scan camera 83, which likewiseimages the sensing volume conveyor belt 32.

The lower right out-feed end line-scan camera 80 is operativelyconnected to an image processor, collecting the line-scan data. Theimage processor determines a parameter value of the first item 20A and aparameter value of the second item 20B being transported through thesensing volume.

In an embodiment, the image processor is the indicia reader. After theindicia reader collects the line-scan data corresponding to the firstitem 20A, it attempts to identify the first item's indicium 24A on thefront side 21 of the first item 20A. In the illustrated case, there isno identification code on the front side of the item, so in operationthe indicia reader will fail to identify the first item's indicium 24Abased on the front side image. However, the indicia reader, receivingline-scan data from either the lower right out-feed end line-scan camera80 or the upper right out-feed end line-scan camera 81, may successfullycapture and identify the second item's indicium 24B.

A lower right in-feed end line-scan camera 82 has a field of viewfocused on a first lower right in-feed end line-scan mirror 95. Thefirst lower right in-feed end line-scan mirror 95 reflects light from asecond lower right in-feed end line-scan mirror 96, which reflects lightfrom a third lower right in-feed end line-scan mirror 97. The thirdlower right in-feed end line-scan mirror 97 reflects light off of thesensing volume conveyor belt 32. Thus, the lower right in-feed endline-scan camera 82 focuses its field of view on the sensing volumeconveyor belt 32, capturing line-scan data about the first item 20A andthe second item 20B being transported in the direction of motion alongthe sensing volume conveyor belt 32. After the indicia reader collectsthe line-scan data corresponding to the first item 20A, it identifies anindicium 24A on the left side 23 of the first item 20A.

In an embodiment, the line-scan cameras may be triggered by signalsderived from a transport location physical sensor to capture a line-scandatum once for every five thousandths of an inch of travel of theconveyor belt 32. That is, when using an encoder having a 1 milinterval, each five intervals will constitute one system count, and oneline scanned image will be captured.

Turning to FIG. 3B, right side camera optics are illustrated andinclude, but are not limited to, the lower right in-feed end line-scancamera 82 and the lower right out-feed end line-scan camera 80. Theright side camera optics capture light from the illumination source 40reflected back into the field of view of the right side camera optics onone or more line-scan mirrors. The line-scan mirrors shown in FIG. 3Binclude the second lower right out-feed end line-scan mirror 93, thethird lower right out-feed end line-scan mirror 94, the second lowerright in-feed end line-scan mirror 96, and the third lower right in-feedend line-scan mirror 97, though more or fewer mirrors can be includeddepending on the specific application contemplated.

FIG. 3B also shows the upper right out-feed end line-scan camera 81 andthe upper right in-feed end line-scan camera 83 imaging the sensingvolume conveyor belt 32, and when the in-feed conveyor belt 30 deliversthe first and second items 20A and 20B to the sensing volume conveyorbelt 32, these line-scan cameras will image the items as well.Eventually, the first and second items 20A and 20B will be out of sightof the upper right out-feed end line-scan camera 81 and the upper rightin-feed end line-scan camera 83 when they are passed along to theout-feed conveyor belt 34.

In an embodiment, the line-scan cameras may be mounted horizontally toreduce dust build-up on the camera lenses. Folding mirrors may be usedto provide selected field of view geometries to allow these horizontallymounted cameras to observe the sensing volume from different angles.

To achieve a desired depth of focus for each line-scan camera along witha fine image resolution to read indicia, the optical path for eachline-scan camera should be several feet from each item 20 in the sensingvolume. To allow for long optical paths without unduly expanding thesize of the system 25, each line-scan camera's optical path may befolded, for example by line-scan mirrors 93, 94, 96, and 97.

Because the width of the field of view for each line-scan camera expandslinearly as the optical distance from the line-scan camera increases,line-scan mirrors that are optically closer to the first item 20A andsecond item 20B may be wider than the belt width in the line scandirection. As will be appreciated, for an imaging field at a 45 degreeangle to the belt, the field width is √2 times the belt width, and themirror must be sufficiently wide to subtend that field. However, becauseeach line-scan camera only images a narrow line sensing volume, aboutfive thousandths of an inch in certain embodiments, each line-scanmirror can be very short in the perpendicular direction. In someembodiments, each line-scan mirror is just a fraction of an inch tall.The line-scan mirrors are made of glass about one quarter of an inchthick and about one inch tall. In a device having a 20 inch wide sensingvolume, the line scan mirrors may have widths from about eight inches toabout thirty inches wide, depending on for what portion of the sensingvolume that scan is responsible. The line-scan mirrors allow the opticalpaths for the bottom, top, and side perspectives of the fields of viewof the line-scan cameras to be folded, while maintaining relativelynarrow top and side walls, about seven inches thick in an embodiment.

Each line-scan camera produces line-scan data from light reflected offof the items 20 traveling through the sensing volume. In an embodiment,with the nominal speed of all of the conveyor belts and imagingresolution, the line-scan cameras operate at about three thousand twohundred lines per second, corresponding to exposure times of about threehundred microseconds. With typical line-scan camera technology, theseshort exposure times necessitate fairly bright illumination to yieldhigh-contrast images. For reasonable energy and illuminationefficiencies, an illumination source 40 may be selected to provideintense illumination with low divergence, focused along each line-scancamera's optical perspective.

FIG. 3C illustrates the right side camera optics. The right side cameraoptics include, but are not limited to, the lower right out-feed endline-scan camera 80, the upper right out-feed end line-scan camera 81,the lower right in-feed end line-scan camera 82, and the upper rightin-feed end line-scan camera 83, which are each connected to the lowerhousing 26 of the system 25. The right side camera optics are shownfocused using line-scan mirrors. In this embodiment, the first lowerright out-feed end line-scan mirror 92 reflects light from the secondlower right out-feed end line-scan mirror 93, which reflects light fromthe third lower right out-feed end line-scan mirror 94, which reflectslight from the sensing volume conveyor belt 32. Furthermore, the firstlower right in-feed end line-scan mirror 95 reflects light from thesecond lower right in-feed end line-scan mirror 96, which reflects lightfrom the third lower right in-feed end line-scan mirror 97, whichreflects light from the sensing volume conveyor belt 32. Light falls onthe sensing volume conveyor belt 32 from the illumination source 40mounted on the upper housing 28.

When the first item 20A and the second item 20B exit the out-feed end ofthe in-feed conveyor belt 30, they enter the in-feed end of the sensingvolume conveyor belt 32 and pass through the fields of view of the rightside camera optics, line-scan data is generated which corresponds to thefirst item 20A and the second item 20B. The first item 20A, bearing theindicium 24A, and the second item 20B, bearing the indicium 24B, exitsthe sensing volume when they are transported from the sensing volumeconveyor belt 32 and onto the in-feed end of the out-feed conveyor belt34. The multiple line-scan cameras, each with its own perspective,capture multiple images of the first item 20A and the second item 20Bbefore they exit the sensing volume. The line-scan data generated isused by the system 25 to recognize parameters for each item as discussedfurther below.

An upward looking line-scan camera 88 is mounted on the lower housing26, as illustrated in FIG. 4A. In this figure, the item 20 travels fromleft to right along the in-feed conveyor belt 30 through the sensingvolume 240. A belt gap 36 is provided between the in-feed conveyor belt30 and the sensing volume conveyor belt 32. Upward looking line-scancamera illumination source 41 provides an intense illumination of thebelt gap 36 with low divergence, allowing upward looking line-scancamera 88 to yield a high-contrast image.

The upward looking line-scan camera 88 produces images from light,traveling through the belt gap 36, and onto the upward looking line-scanmirror 98. The light is generated by the upward looking line-scan cameraillumination source 41 and is reflected off of item 20 as it travelsfrom in-feed conveyor belt 30 over belt gap 36 and onto the sensingvolume conveyor belt 32.

In addition to providing an image of item 20 for later analysis by theindicia reader, the upward looking line-scan camera 88 providesunobstructed images of the bottom of item 20. While analysis by theindicia reader can identify an indicium on the bottom of item 20, thedimensioning sensor uses the unobstructed images of the bottom of item20 to help refine the measurements of item 20. Thus, in embodimentsincluding upward looking line-scan camera 88, items of disparate heights(such as first item 20A and second item 20B shown in FIGS. 3A and 3C)can be placed adjacent to one another on the in-feed conveyor belt 30without the item isolator treating the items of disparate heights as asingle item having a more complex geometry.

As shown in FIG. 4B, the upward looking line-scan camera opticalcomponents, including upward looking line-scan camera illuminationsource 41, upward looking line-scan mirror 98, and upward lookingline-scan camera 88, are located within the lower housing 26 of thesystem 25. In the illustrated embodiment, the optical path of upwardlooking line-scan camera 88 is folded only once, off of upward lookingline-scan mirror 98. In other words, light reflected off of item 20 asthe light crosses through the belt gap 36 is reflected off of upwardlooking line-scan mirror 98 to upward looking line-scan camera 88. Asdescribed previously, the item 20 is positioned over the belt gap 36when the item 20 is transferred from the in-feed conveyor belt 30 to thesensing volume conveyor belt 32.

As will be appreciated, the upward looking camera is a dark fielddetector. That is, in the absence of an object in its measurement area,it will receive little or no reflected light, and the image will bedark. When an object is present in the measurement area, reflected lightfrom the illumination source 41 will be reflected back to the camera. Incontrast, the light curtain described above is a bright field detector.When no object is present, the image is bright, while when an object ispresent, the image field is shaded by the object, causing it to appearas a dark object in the detector.

Working in conjunction with each other, the two systems allow fordetection and measurement of objects that may be difficult to detectwith one or the other approach. For example, an object that isrelatively dark, and/or a poor reflector may be difficult for the upwardlooking camera to distinguish from the dark background field. Similarly,an object that is relatively transparent may not produce sufficientcontrast to be detected by the light curtain. The inventors havedetermined that a good rate of object singulation can be obtained whenusing the two sensors in combination with the laser stripe generator 119described below.

As seen in FIG. 5A, a transport location sensor includes, but is notlimited to, an in-feed conveyor belt 30, a sensing volume conveyor belt32, an out-feed conveyor belt 34, and a transport location physicalsensor 122.

A weight sensor, also seen in FIG. 5A, includes, but is not limited to,at least one load cell (175A-D in FIG. 12), previously mentioned in thecontext of FIG. 2B. In an embodiment, the weight sensor includes fourload cells. The set of four load cells supports the sensing volumeconveyor belt 32 and its associated mechanical structure (motor,rollers, the belt, etc.). In some embodiments, the weight sensor alsoincludes three object sensors, shown herein as an in-feed conveyor beltobject sensor 173A, a sensing volume entrance object sensor 173B, and asensing volume exit object sensor 173C. In some embodiments, each objectsensor is placed about two tenths of an inch above the transportlocation sensor 122. In some embodiments, the object sensors are lightsources and photodetector pairs in which the optical path between thelight source and the photodetector is interrupted in the presence of anobject, such as item 20. Other object sensors are well known in the art,and can be used depending on the specific application contemplated.

Item 20 is transported toward the sensing volume along the in-feedconveyor belt 30 of the transport location sensor. In an embodiment, asthe item 20 approaches the sensing volume, the in-feed conveyor beltobject sensor 173A detects that item 20 is about to enter the sensingvolume. Item 20 passes over belt gap 36 as it is transferred fromin-feed conveyor belt 30 to sensing volume conveyor belt 32, and thesensing volume entrance object sensor 173B ascertains that the item 20has entered the sensing volume. Similarly, the sensing volume exitobject sensor 173C detects when item 20 exits the sensing volume and istransferred from sensing volume conveyor belt 32 to out-feed conveyorbelt 34. However, the existence and particular location of each objectsensor varies depending on the specific application contemplated.

When, as in FIG. 5A, no items are located on sensing volume conveyorbelt 32, the load cells measure the total weight of the sensing volumeconveyor belt 32. Then, as one or more items 20 are transferred to thesensing volume conveyor belt 32, the load cells measure the weight ofthe sensing volume conveyor belt 32 and the weight of the one or moreitems 20. Each load cell converts the force (weight) into a measurableelectrical signal, which is read out as a load cell voltage. Since theelectrical signal output of each load cell is on the order ofmillivolts, the signals of the load cells are amplified and digitized byload cell amplifiers (not shown).

As seen in FIG. 5B, the weight sensor includes, but is not limited to,the set of object sensors (173A, 173B, and 173C) and the load cells. Thesensing volume entrance object sensor 173B is located just inside theupper housing 28 of the sensing volume and above the belt gap (indicatedin FIG. 4A by reference number 36) between in-feed conveyor belt 30 andsensing volume conveyor belt 32. Similarly, the sensing volume exitobject sensor 173C is located just inside the upper housing 28 of thesensing volume and above the out-feed conveyor belt 34. The in-feedconveyor belt object sensor 173A is located above the in-feed conveyorbelt 30 upstream of the sensing volume. While FIG. 5B depicts thein-feed conveyor belt object sensor 173A as being close to the sensingvolume, the distance between the in-feed conveyor belt object sensor173A and the sensing volume can vary depending on the specificapplication contemplated.

FIG. 5B also shows that load cells 175A and 175C are located inside thelower housing 26 of the sensing volume. Load cells 175B and 175D (asdepicted in FIG. 12) are not visible in this view as they are blocked byload cells 175A and 175C, respectively. The load cells support sensingvolume conveyor belt 32 and its associated mechanical parts, enablingthe set of load cells to measure the weight of the sensing volumeconveyor belt 32 and items thereon, if any.

As seen in FIG. 5B, the transport location physical sensor 122, in theillustrated embodiment a rotary encoder, is located close to a load cell175C. The transport location physical sensor 122 is connected to thesensing volume conveyor belt 32 and a digital counter in one of thesystem processors. As the sensing volume conveyor belt 32 is rotated bythe motor, the encoder wheel turns, allowing the transport sensorprocessor to record the movement of the sensing volume conveyor belt 32.The displacement of the conveyor belt from an arbitrary startinglocation is defined as the transport system location. The transportsensor processor generates the transport system location on the conveyorbelt for each transport sensor pulse generated by the transportlocations physical sensor 122, though as mentioned above, in practice anumber of sensor pulses may together constitute a system count, in orderto provide appropriate intervals. The signals from the transportlocation physical sensor 122 are also used to trigger the line-scancameras described herein to take images. In an embodiment, the transportsystem location is the along-track co-ordinate of the item, wherein thealong-track co-ordinate system is established in keeping with a virtualsensing volume conveyor belt that is infinitely long. When the system 25receives the object position of the item 20 from the in-feed conveyorbelt object sensor 173A it generates the transport system locationcorresponding with the along-belt co-ordinate of the item 20.

As illustrated in FIGS. 6A and 6B, an embodiment of the dimension sensorincludes, but is not limited to, a laser stripe generator 119, at leastone laser mirror (shown herein as a first laser mirror 99, a secondlaser mirror 100 and a third laser mirror 101), an area camera 152, oneor more area camera mirrors (shown herein as first area camera mirror 48and second area camera mirror 49), an upward looking line-scan camera(shown with reference number 88 in FIGS. 4A and 4B), and at least oneparameter processor (not shown) for processing the parameter valuesgenerated from the area-camera images from the area camera 152 andline-scan data from the upward looking line-scan camera.

Laser stripe generator 119 projects a laser stripe upward to the firstlaser mirror 99. As will be appreciated, a number of types of opticalelements are capable of converting a laser beam into a stripe,including, for example, a cylindrical lens, a prism, conic mirrors, orother elements may be used. The laser stripe is reflected from the firstlaser mirror 99 to the second laser mirror 100 and onto the third lasermirror 101. The third laser mirror 101 projects the laser stripedownward from the top of the sensing volume onto the sensing tunnelconveyor belt 32. In a particular embodiment, laser stripe generator 119uses a holographic optical element and a laser diode to generate thelaser stripe. In an embodiment, the laser diode is an infrared laserdiode, and the area camera 152 is a CCD camera configured to detectinfrared radiation. In a particular embodiment, a low pass filter or aband pass filter configured to preferentially allow infrared radiationto pass while attenuating an amount of visible light is placed over theCCD.

Item 20 is transported through the system from left to right along thetransport system in the direction of motion from the in-feed conveyorbelt 30 to the sensing volume conveyor belt 32 to the out-feed conveyorbelt 34. It is transferred from in-feed conveyor belt 30 to sensingvolume conveyor belt 32, which transports it through the sensing volume.Area camera 152 has a pyramid-shaped field of view which looks down onsensing tunnel conveyor belt 32 after it is folded by first area cameramirror 48 and second area camera mirror 49. While the field of view ofarea camera 152 is depicted in FIGS. 6A and 6B as being folded by firstand second area camera mirrors 48 and 49, the number of mirrors used tofold the field of view of area camera 152 is merely by way of example,and can vary depending on the specific application contemplated. Thelaser stripe is projected onto the sensing volume conveyor belt 32within the field of view of area camera 152. Item 20 is transportedthrough sensing volume on sensing volume conveyor belt 32, passingthrough the point at which the laser stripe is projected onto thesensing volume conveyor belt 32 from above. At that point, the areacamera captures area-camera images of item 20 and the laser stripereflecting off of the item.

In the embodiment illustrated in FIG. 7A, the system 25 includes aleft-side downward looking line-scan camera 89 and a right-side downwardlooking line-scan camera 90. The field of view of left-side downwardlooking line-scan camera 89 is folded by left-side downward lookingline-scan camera mirrors (first left-side downward looking line-scancamera mirror 105, second left-side downward looking line-scan cameramirror 106, third left-side downward looking line-scan camera mirror107, and fourth left-side downward looking line-scan camera mirror 108)before being projected down onto sensing volume conveyor belt 32 at anangle that captures the top side of item 20 and the back-side of item 20as the item 20 passes through the sensing volume front-side first fromthe in-feed conveyor belt 30 to the sensing volume conveyor belt 32 tothe out-feed conveyor belt 34, as shown in the illustrated embodiment.

The field of view of right-side downward looking line-scan camera 90 isfolded by right-side downward looking line-scan camera mirrors (firstright-side downward looking line-scan camera mirror 123, secondright-side downward looking line-scan camera mirror 124, thirdright-side downward looking line-scan camera mirror 125, and fourthright-side downward looking line-scan camera mirror 126) before beingprojected down onto sensing volume conveyor belt 32 at an angle thatcaptures images of the top side of item 20 and the front-side of item 20as the item 20 passes through the sensing volume front-side first.

Right-side downward looking illumination source 128 provides an intenseillumination of the sensing volume conveyor belt 32 with low divergence,allowing right-side downward looking line-scan camera 90 to yield ahigh-contrast image. Similarly, left-side downward looking illuminationsource (not shown in FIG. 7A) provides an intense illumination of thesensing volume conveyor belt 32 with low divergence, allowing left-sidedownward looking line-scan camera 89 to yield a high-contrast image.

As shown in FIG. 7B the field of view of left-side downward lookingline-scan camera 89 is folded first by first left-side downward lookingline-scan camera mirror 105, then by second left-side downward lookingline-scan camera mirror 106. It is then further folded by thirdleft-side downward looking line-scan camera mirror 107 and fourthleft-side downward looking line-scan camera mirror 108. Fourth left-sidedownward looking line-scan camera mirror 108 projects the field of viewof left-side downward looking line-scan camera 89 down onto the sensingvolume conveyor belt 32. Item 20 is transported along in-feed conveyorbelt 30 onto sensing volume conveyor belt 32 which will transport theitem 20 through the sensing volume after it completes its journey overthe in-feed conveyor belt 30. As item 20 is transported through thesensing volume, it is brought into the field of view of left-sidedownward looking line-scan camera 89, and the left-side downward lookingline-scan camera 89 captures images in the form of line-scan data of theitem 20.

Similarly, the field of view of right-side downward looking line-scancamera is folded first by first right-side downward looking line-scancamera mirror, then by second right-side downward looking line-scancamera mirror. It is then further folded by third right-side downwardlooking line-scan camera mirror 125 and fourth right-side downwardlooking line-scan camera mirror 126. Fourth right-side downward lookingline-scan camera mirror 126 projects the field of view of right-sidedownward looking line-scan camera down onto the sensing volume conveyorbelt 32. As item 20 is transported through the sensing volume, it isbrought into the field of view of right-side downward looking line-scancamera, and the right-side downward looking line-scan camera capturesimages, line-scan data, of the item. Once the item 20 has completed itsjourney over the sensing volume conveyor belt, it passes onto theout-feed conveyor belt 34. In some embodiments, some parameter sensorsare able to continue sensing the item 20 as it travels on the out-feedconveyor belt 34.

Information/Data Flow

FIG. 8 illustrates a dataflow for use in an embodiment of a system 25,organized as moving from top horizontal slices to bottom horizontalslices of an asynchronous, data driven architecture of the system. Thatis, in the embodiment, there may be no universal clock within thesystem, sensors and processors output their results as soon as the datais available, and the data flows are, in general, unidirectional. In anembodiment, information is conveyed between processes by TCP/IP networkmessages, and within processes via shared memory.

As will be discussed in greater detail below, FIG. 9 illustrates thesame elements grouped in parallel, sensing sensors/processes, namely atransport location sensor 120, one or more indicia reader(s) 130, adimension sensor 150, an item isolator 140, and a weight sensor 170, toemphasize that each physical sensor and associated parameter processormay operate autonomously from the other physical sensors and parameterprocessors. FIG. 8, on the other hand, is organized so that data flowsfrom the data source level to the parameter processor level to thegeo-parameter matching level to the final stage, product identification,which is the stage where the items that have been sensed in the sensingvolume are either identified as products or flagged as exceptions. Eachlevel in the hierarchy of an embodiment will be addressed in turn below.

Data Sources

The first data source is a transport system location sensor 120,typically comprising a transport system location physical sensor 122 anda transport sensor processor 127, as shown in FIG. 9. In one embodiment,transport system location physical sensor 122 is a rotary encoderattached to a belt roller. As shown in FIG. 9, the initial sensing datafrom transport system location physical sensor 122 is a count increment,the transport sensor pulse D147 (each of which may represent more thanone sensor pulse), which is sent to a transport sensor processor 127.Transport sensor processor 127 performs a simple summation and scalingprocess to convert transport sensor pulses D147 into transport systemlocation values D148. Transport system location values are distributedto each of the other parameter processors so that the parameterprocessors can associate a transport system location with each measuredparameter value. In some embodiments, transport sensor processor 127also uses the transport sensor pulses D147 to generate line-scan cameratrigger signals D142 and area camera trigger signals D151 for thevarious line-scan cameras 132 and an area camera 152 respectively. Bytriggering the cameras based on transport system movement, rather thanat fixed time intervals, the system may avoid repeatedly recordingimages of the same field.

The second data source illustrated in FIG. 8 is area camera 152. Areacamera 152 is positioned to observe the path of a line of laser lightprojected downward towards sensing volume conveyor belt and any itemsthereon. As described previously, there is a known angle between thelaser projector and the area camera which causes the image of the lineof laser light in the camera to be displaced perpendicular to the line,in proportion to the height of the item on which the line is projected.The data from area camera 152 is sent to item isolating parameterprocessor 144 and dimension estimator 154.

The third data source illustrated in the system illustrated in FIG. 8 isa set of line-scan cameras 132. The primary function of the line-scancameras 132 is to provide input to indicia parameter processor(s) 134.In an embodiment there are eleven line-scan cameras 132, which have beendetermined by the inventors to provide full coverage of the sensingvolume, with adequate imaging resolution. Other embodiments can beimplemented with fewer or greater numbers of line-scan cameras,depending on the performance goals of the designer, the size and shapeof the sensing volume, the resolution of the cameras and other factors.

The fourth illustrated data source is an in-motion scale 172 comprising,in an embodiment, three object sensors 173A, 173B and 173C (shown in atleast FIG. 5B) and four analog load cells 175A, 175B, 175C, and 175D(shown in at least FIG. 12). The load cells are disposed in the loadpath supporting the sensing volume conveyor belt. Each load cellgenerates an electrical signal in proportion to the compression forceapplied the load cell. The signals from all the load cells and all theobject sensors are sent to weight generator 174.

The data sources described above are included in one particularembodiment and should not be construed as exhaustive. Other data sourcescan easily be included in a system of this type, depending on theparameters to be monitored. For example, infrared sensors could providemeasurements of item temperature or color imagers could be used as datasources to measure a spatial distribution of colors on package labels.

Parameter Processors

Returning to FIG. 8, the second stage of the data flow architecturecontains the parameter processors. Each data source has one or moreassociated parameter processor(s) to transform the initial sensing datainto a parameter value, which are then used by an item identificationprocessor to identify the item. In an embodiment, these parameterprocessors comprise an item isolating parameter processor 144, adimension estimator 154, an indicia parameter processor 134, and aweight generator 174. In FIG. 8, an optional image processor 183 isdepicted as a parameter processor.

The first processor shown in FIG. 8 is the item isolating parameterprocessor 144. Functionally, item isolating parameter processor 144includes an item distinguishing system, an item locator and an itemindexer. The item isolating parameter processor 144 allows the system tooperate on multiple items in close proximity to each other in thesensing volume. The item isolating parameter processor 144, in someembodiments, uses data collected near the entrance to the sensing volumeand performs four functions:

A. first, the item isolating parameter processor 144 recognizes that anobject (which may be one or more items) has entered the sensing volume;

B. second, the item distinguishing system determines how many distinctitems make up the object that entered the sensing volume;

C. third, the item indexer assigns a Unique Item Index value (UII) toeach distinct item. The UII is simply a convenient name for theparticular item; and

D. fourth, the item locator associates a two-dimensional location in theplane of the bottom of the sensing volume (for example, the plane of theconveyor belt) with each item that has been identified and assigned aUII.

If all items entering the sensing volume are well separated in thealong-transport direction (i.e., they are singulated), there may be noneed for the item isolating parameter processor 144, as all parametervalues will be associated with the only item in the sensing volume. Whenitems are not singulated, however, the item isolating parameterprocessor 144 determines how many items are in close proximity to eachother and assigns each item a UII associated with its transport systemlocation.

Item isolating parameter processor 144 outputs a UII and transportsystem location D148 when it has isolated an item. The unique item index(UII) value, as its name suggests, may simply be a sequentiallygenerated index number useful for keeping track of the item. This datais provided to dimension estimator 154 and an item description compiler200.

Although item isolation may be a separate logical function in thesystem, the computer processing embodiment of item isolating parameterprocessor 144 in particular embodiments may work in close conjunctionwith dimension estimator 154, with internal data being transferred backand forth between the functions. The item isolating parameter processor144 in this approach functions as part of the dimension estimator 154processing to recognize the difference between one large item and anaggregation of multiple smaller close together items, and to instructthe dimension estimator 154 to estimate the dimensions of the one ormore than one item respectively.

The dimension estimator 154 receives data from area camera 152, from aselected line-scan camera 132 (the upward-looking camera in oneembodiment) and from the transport sensor processor, which includes thetransport system location sensor 120. In addition, working inconjunction with the item isolating parameter processor 144, dimensionestimator 154 receives information about how many items are in the areacamera's field of view and where they are. It will be understood thatwhile isolation and dimensioning may be logically distinct functions,they may share a number of processing operations and intermediaryresults and need not be entirely distinct computer processes.

In one embodiment, dimension estimator 154 estimates the length, height,and width of the dimensions of the item, ignoring the fact that the itemmay have a complex (non-rectangular) shape. That is, in this approach,estimator 154 calculates a smallest rectangular box into which the itemwould fit. The dimension estimator 154 can be configured to estimateparameter values regarding the general shape of the item (cylindrical,rectangular solid, necked bottle shape, etc.), the item's orientation onthe transport system, and details concerning the item'sthree-dimensional coordinates in the sensing volume. The calculatedparameter values, along with the transport system location of the itemto which they apply, are sent to the item description compiler 200 assoon as they are calculated.

There is one indicia parameter processor 134 associated with eachline-scan camera 132. Together they form an indicia reader 130, as shownin greater detail in FIG. 10. As will be appreciated, the indiciaparameter processors may be individual devices or may be virtualprocessors, for example respective modules running on a commonprocessor. Indicia parameter processor 134 examines the continuous stripimage produced by line-scan camera 132 until it identifies the signatureof an indicium (typically a bar code such as a UPC). Furthermore, theindicia parameter processor 134 attempts to convert the indicia imageinto the underlying code, which can later be compared by the itemdescription processor with the product description database to determinea product code that uniquely identifies the product. In addition tooutputting the product code to the item description compiler 200, theindicia parameter processor 134 outputs the apparent location of theindicia in camera-centric coordinates.

As will be appreciated, additional methods are available for determiningan indicia parameter. For example, many bar codes include numericalindicia in addition to the coded numbers that make up the code. In thisregard, optical character recognition (OCR) or a similar approach may beused to recognize the numbers themselves, rather than decoding the bars.In the case where the indicia are not bar codes at all, but ratherwritten identifying information, again OCR may be employed to capturethe code. In principle, OCR or other word recognizing processes could beused to read titles or product names directly as well.

Where, as with bar codes, there are a limited number of possiblecharacters and a limited number of fonts expected to be encountered,simplifying assumptions may be made to assist in OCR processes and allowfor a character matching process. A library may be built, incorporatingeach of the potential characters or symbols and rather than a detailedpiece-by-piece analysis of the read character shape, the shape can becompared to the library members to determine a best match.

Furthermore, because in a typical environment there are fewer likelycombinations than there are possible combinations, it is possible that apartially readable code can be checked against likely codes to narrowdown the options or even uniquely identify the code. By way of example,for a retailer stocking tens of thousands of items, each having a 10digit UPC, there are 10¹⁰ possible combinations but only 10⁴combinations that actually correspond to products in the retailer'ssystem. In this case, for any given partially read code, there may beonly one or a few matches to actual combinations. By comparing thepartial code to a library of actually-in-use codes, the system mayeliminate the need to generate an exception, or it may present anoperator with a small number of choices that can be evaluated, which maybe ranked by order of likelihood based on other parameters or otheravailable information. Alternately, the partial match information may bepassed as a parameter to the product identification module and evaluatedalong with other information to determine the correct match. In anembodiment, more than one bar code reader software module may beemployed using different processing algorithms to process the same readdata, and the results from each module can be compared or otherwiseintegrated to arrive at an agreed upon read, or on a most-likely readwhere there is no agreement.

For weight parameters, the in-motion scale 172 generates a signalproportional to the sum of the weights of the items on the scale. Forsingulated items, where only one item is in the active sensing volume ata time, the weight generator 174 may sum the signals from the in-motionscale 172, the load cells in the illustrated embodiment, and apply atransformation to convert voltage to weight. For non-singulated items,where more than one item can be in the sensing volume simultaneously(i.e., closely spaced along the sensing volume conveyor belt), weightgenerator 174 has two opportunities to estimate the weight of individualitems: immediately after the item enters the sensing volume, andimmediately after the item exits the sensing volume. The object sensorsof the in-motion scale 172 are provided to inform weight generator 174when items have entered or exited the in-motion scale 172. The objectsensors are incorporated into the in-motion scale 172 so its operationmay be conducted independently of other parameter sensors.

As with the data sources, this list of parameter processors listed aboveis by way of example, not an exhaustive listing. For instance, FIG. 8includes an optional image processor 183. Furthermore, it should beappreciated that any one of the parameter processors described hereinmay be omitted in particular embodiments. For example, where the size,shape and indicia parameters are sufficient to identify objects in thesensing volume, there may be no need to include weight parameters.

Geometric-Parameter Matching

Geometric-parameter matching is the process of using the known geometryof the various physical sensors and the fields-of-view at which theycollected their initial sensing data to match the measured parametervalues with the item to which the parameter values apply. The itemdescription compiler 200 is the processor that collects all theasynchronous parameter data and makes the association with theappropriate item. As the name suggests, the output of the itemdescription compiler 200 may be referred to as an item descriptionassociated with the item. The item description is a compilation ofparameter values collected by parameter processors for an item measuredin the sensing volume.

After the item description compiler 200 has built an item descriptionfor a particular item, the item description may be passed to an itemidentification processor 300, which performs the product identificationfunction. In practice, while there may be a number of available itemdescription fields, it is possible to identify items without completingevery field of the item description. For example, if a weightmeasurement was too noisy or the indicium was hidden from view, smudged,or otherwise unreadable, the item description may still be sent to theitem identification processor 300 rather than being stuck at thegeometric-parameter matching level at the item description compiler 200.The item description compiler 200 can decide, for example, that havingonly the digital indicia data is enough data to pass on to the itemidentification processor 300, or it can determine that the item hasmoved out of the sensing volume and no more parameter values will beforthcoming from the parameter processors.

Product Identification

By way of example, item identification processor 300 may receive an itemdescription from item description compiler 200. Using the parametervalues data in the item description, the item identification processorforms a query to a product description database, which in turn returns aproduct identification and a list of the expected parameter values forthat product, along with any ancillary data (such as standard deviationson those parameter values).

Item identification processor 300 decides if the item matches theproduct with a high enough degree of certainty. If the answer is yes,the product identification datum D233 is output; if the answer is no,the item may be identified with an exception flag D232. Theidentification/exception decision logic can vary from simple to complexin various embodiments. At the simple end of the logic scale the itemidentification processor could flag any item for which the weight didnot match the weight of the product described by the UPC. At the complexend of the logic scale the item identification processor can incorporatefuzzy logic which is a form of non-Boolean algebra employing a range ofvalues between true and false that is used in decision-making withimprecise data, as in artificial intelligence systems.

Optionally, various exception handling routines 320 can be invoked.These routines can be as rudimentary as doing nothing or lighting alight for a human to observe, or they can be more complex. For example,item identification processor 300 could be instructed to act as thoughthe read indicium is in error by one or more digits and to re-query theproduct description database with variations on the read indicium.

Optionally, each successful product identification can be used to updatethe product description database. That is to say, every successfulidentification increases the statistical knowledge of what a productlooks like to the system 25. Also optionally, information relating toexception flags D232 can also be added to the history database 350 forimprovement of the system 25.

Asynchronous Information Flow and Processing System

FIG. 9 illustrates an embodiment of a data flow for the same elements asshown in FIG. 8, with a slightly different notional grouping andarrangement. The illustrated data sources are a transport locationsensor 120, one or more indicia reader(s) 130, a dimension sensor 150,an item isolator 140, and a weight sensor 170, to emphasize that eachphysical sensor and associated parameter processor operates autonomouslyfrom the other physical sensors and parameter processors.

The transport system location sensor 120, in some embodiments, includesthe transport system location physical sensor 122 and a transport sensorprocessor 127. In some embodiments, such as the one shown in FIG. 9, thetransport location physical sensor 122 takes the form of a rotaryencoder associated with a belt roller. The initial sensing data fromtransport system location physical sensor 122 is a count increment, thetransport sensor pulse D147, which is sent to the transport sensorprocessor 127. The transport sensor processor 127 then performs asummation and scaling process to convert transport sensor pulses D147 totransport system location values D148. As described above, the systemmay treat the conveyor belt as being essentially continuous and thetransport system location is essentially the distance along the(continuous) conveyor belt from some arbitrary starting point.

In a particular embodiment, this distance is measured in increments ofabout five-thousandths of an inch, and may be referred to as anx-coordinate. In an embodiment, transport sensor processor 127 also usesthe transport sensor pulses D147 to generate line-scan trigger signalsD142 and area camera trigger signals D151 for the various line-scancameras and an area camera respectively. By triggering the cameras basedon transport system movement, rather than at fixed time intervals, thesystem 25 may avoid repeatedly recording images of the same field. Thus,the output of the transport sensor processor 127 includes the line-scantrigger D142, the area camera trigger D151, and the transport systemlocation D148.

Aside from a set of conventional dedicated motor controllers, transportsensor processing includes converting input belt commands D50 (e.g.,stop, start, speed) received from the weight sensor 170, into motorcontroller signals; converting the transport system sensor pulses D147into a transport sensor location values D148; and transmitting thatvalue to the various parameter processors, including without limitationthe item isolating parameter processor 144, the dimension estimator 154,the indicia parameter processor 134, the weight generator 174, and,optionally, the image processor 183, wherein each parameter process maybe as illustrated and described in relation to FIG. 8, above.

It will be noted that transport sensor processor 127 may communicatedirectly with the various cameras to send them frame triggers.

The transport system location D148 output from the transport systemlocation sensor 120 is provided to the item isolator 140, the dimensionsensor 150, the indicia reader 130, the weight sensor 170, any optionalimage processors 183 (shown in FIG. 8), and the item descriptioncompiler 200.

A set of one or more line-scan cameras, which are included in theindicia reader 130, are triggered by the line-scan trigger D142. Asshown in FIG. 9, the line-scan trigger D142, triggers the line-scancameras to produce line-scan data which initiates activity within theitem isolator 140, the dimension sensor 150, and the indicia reader 130.The activity initiated by the line-scan trigger D142 will be fullydescribed below in the descriptions of FIG. 10, which describes theindicia reader 130, and FIG. 11, which describes the item isolator 140and the dimension sensor 150. Similarly, the area camera trigger D151may trigger activity in the area cameras which output area camera datato item isolator 140 and the dimension sensor 150, which is described inmore detail in accordance with FIG. 11.

In an embodiment, there is one indicia reader 130 associated with eachline-scan camera, which may be a virtual indicia reader. Indicia reader130 examines the continuous strip image produced by its line-scan camerauntil it identifies the signature of a pre-determined indicium(typically a bar code such as a UPC) at which time it decodes theindicia image into a digital indicia value D159. Additionally, indiciareader 130 outputs the apparent location D236 of the indicia incamera-centric co-ordinates. The digital indicia data D159, itemlocation on the transport system D148 and indicia location incamera-centric co-ordinates D236 are transferred from the indicia reader130 to the item description compiler 200.

In some embodiments, indicia reader 130 may, on occasion, receive imageretrieval requests D149 from the item description compiler 200, wherebyindicia reader 130 extracts an image subframe D234 containing theindicia from the continuous strip image. The extracted images of theidentified indicia are transferred to a history database 350. Thehistory database 350 is an optional element of the system that may beused for post-analysis, and image retrieval is similarly optional.

Note that each of the line-scan cameras may detect indicia at differenttimes, even for a single item. For example, items lying on the sensingvolume conveyor belt with an indicium pointing up are likely to have atleast two line-scan cameras record the image of the indicium (forexample, the left-side and right-side downward looking line-scancameras), possibly at different times. These two images of the UPC willbe processed as each datum arrives at its respective indicia reader,with the two UPC values and associated camera-centric co-ordinates beingsent to the item description compiler 200 asynchronously.

Returning to FIG. 9, item isolator 140 receives the line-scan cameratrigger D142 and the transport system location D148 from the transportsystem location sensor 120. Item isolator 140 outputs a unique itemindex (UII) value D231 with the associated item's transport systemlocation D148 to the item description compiler 200 only when it hasisolated an item. The UII value is provided internally to the dimensionestimator 154 (shown in FIGS. 8 & 11) and externally to the itemdescription compiler 200 as soon as they are available.

Although a separate logical function in the system, the item isolator140 computer processing in embodiments of the system may work inconjunction with the dimension sensor 150 and/or the light curtainassembly. Essentially, the item isolator A) assists the dimensionestimator 154 (shown in FIGS. 8 & 11) processing to recognize thedifference between one large item and more than one item positionedclose together in the sensing volume, and B) instructs the dimensionestimator 154 to estimate the dimensions of the one or more than oneitem respectively.

The dimension sensor 150 receives the area camera trigger D151, and thetransport system location D148 from the transport system location sensor120. The area camera, which is part of the dimension sensor 150, uponreceipt of the area camera trigger D151, generates area camera imagedata and provides the area camera image data to the dimension estimator154. In addition, working in conjunction with item isolator 140, thedimension sensor 150 collects information about the number of items inthe area camera's field of view and where the items are. The dimensionsensor 150, specifically the dimension estimator, combines multipleframes from area camera 152 to estimate the locus of points that formthe surfaces of each item using a triangulation process. The dimensionsensor 150, including the processing of the dimension estimator isdescribed in greater detail in accordance with FIG. 11.

The dimension sensor 150 further transforms the estimated item surfacesto determine a bounding box for each individual item. That is, itcalculates a smallest rectangular volume that would hold each item. Inan embodiment, the length, height, and width of this bounding box areconsidered to be the dimensions of the item, ignoring anynon-rectangular aspects of its shape. Similarly, a more complex boundingbox may be calculated, treating respective portions of the item as boundby respective bounding boxes. In this approach, each object is renderedas an aggregation of parameters representing box structures, but theoverall shape of the item is somewhat preserved. Collateral parameters,such as the item's orientation and 3-dimensional co-ordinates on thesensing volume conveyor belt, are also calculated in one embodiment.Further, the dimension sensor 150 can, at the discretion of the user,estimate parameter values regarding the general shape of the item(cylindrical, rectangular solid, necked bottle shape, etc.) bycalculating higher order image moments. These parameter values, alongwith the transport system location of the item to which they apply, arethe dimensioning data D166 transmitted to item description compiler 200.As an optional step, the dimension sensor 150 outputs some intermediatedata, such as closed height profiles D247, to history database 350.

In an embodiment, a disambiguation functionality may be included thatprovides additional approaches to handling closely spaced items that areidentified by the system as a single object. In this regard, for eachobject profiled by the dimension sensor, in addition to providing amaster profile for each item, multiple subordinate height profiles maybe generated. The subordinate profiles can be generated, for example, byrunning a blob detection operation over the master profile to determinewhether subordinate regions exist. Where subordinate profiles aredetected, both the master and subordinate profiles may be published withthe item description for use by other subsystems. If no subordinateprofiles are detected, only the master profile is published.

For cases in which subordinate profiles are detected, and multipleindicia are read for the object having subordinate profiles, adisambiguation process based on the subordinate profiles may be run. Inthis process, the subordinate profiles are used along with a limiteduniverse of potential item identifications. In particular, only thoseitem identifications corresponding to the indicia read for the objectare used. Once the universe of potential matches is limited in this way,matching can proceed in accordance with the approaches described inrelation to the several embodiments described herein. If the result ofthis matching process yields subordinate items that are all uniquelyidentifiable, the subordinate items are published in place of themulti-read and the master item is discarded. If unique reads are notobtained the multiple read object may be published for further analysisby the system as is.

Weight sensor 170 is the last sensor shown in FIG. 9. As previouslydiscussed, an embodiment of the weight sensor 170 includes the in-motionscale 172 and weight generator 174 (shown in FIG. 8), which sums thesignals from the in-motion scale and applies a transformation to convertvoltage to weight data. For non-singulated items, where more than oneitem can be in the sensing volume simultaneously (i.e., closely spacedalong the sensing volume conveyor belt), weight sensor 170 has twoopportunities to estimate the weight of individual items: immediatelyafter the item enters the sensing volume, and immediately after it exitsthe sensing volume. The object sensors of the in-motion scale providethe weight sensor 170 with information on when items have entered orexited the in-motion scale, which is used by the weight generator todetermine the weight data D191 corresponding with individual items whenthere are multiple items located on the sensing volume conveyor belt atthe same time. When multiple items overlap as they enter or exit thesensing volume the weight sensors produces an aggregate weight for theoverlapping items. The weight sensor 170 transfers weight data D191,which is the item weight and item's location on the transport system, tothe item description compiler 200. Optionally, the continuous stream ofweight data 191 is sent to the history database 350 in Step D190. Theweight sensor 170 also delivers belt control commands D50 to thetransport system motor controllers, as will be described below.

As indicated in the descriptions of FIGS. 8 and 9, in one embodiment,the item description compiler 200 receives data from all the variousparameter sensors. Item description compiler 200 conductsgeometric-parameter matching, which is the process of using the knowngeometry of the various physical sensors and their fields-of-view tomatch the measured parameter values with the item that was in theirfields-of-view at the moment(s) the measurements were made.

An item description (the output of item description compiler 200) iscompiled by matching the measured parameter value with the item known tobe in the particular sensor's field-of-view. As described above, whereeach sensor's field of view is known, for example relative to a fixedreference point in the transport system, it is possible to associate aninstance of item detection with a particular location. From time to timeit may be useful to calibrate the system by imaging an item having knowngeometry and/or indicia, for example an open box of a known size andhaving indicia located at known locations thereon.

As an example, a line-scan camera looking straight down on the beltmight have a field of view described as a straight line across thesensing volume conveyor belt, with the center of the line at the centerof the sensing volume conveyor belt in the across motion dimension andsix inches downstream from a reference point defined for the itemdescription compiler 200.

In this example, indicia reader 130 determines that UPC 10001101110 wasread starting at 200 pixels from the left end of the line scan camera'sfield of view, at the instant that the transport system location was20,500 inches from its initialization point. Using known informationregarding the camera parameters and the camera's geometric relationshipto the sensing volume conveyor belt, item description compiler 200 candetermine that the UPC was observed 1 inch from the left of the sensingvolume conveyor belt and at a transport system location of 20,494inches. The item description compiler 200 then associates this UPC withthe item (with an arbitrary UII, 2541 as an example) that was observedto be closest to transport system location 20,494 inches. Similarly,when the weight sensor, specifically the weight generator, reports aweight data D191 for an item was loaded onto the in-motion scale attransport system location 20,494, item description compiler 200associates that weight data D191 with item UII 2541.

The geo-parameter matching process is generally more complex than thissimple example, and makes use of knowledge of the full three-dimensionalfield of sensing of each physical sensor. In one embodiment, the fullthree-dimensional geometry of all of the sensor's respective fields ofsensing may be compiled into a library for use by the item descriptioncompiler 200. The library is used by the description compiler 200 toassociate items and sensed parameters. Thus, in an embodiment, it is thefull three-dimensional location of each item (for example a set oftransverse, longitudinal, and rotational coordinates of the item)combined with the item's height, width, and depth that are used in thecompilation of a complete item description of each item. Because no twoitems can exist in the same physical space, transport system locationD148 and the bounding box description of each item may be used by theitem description compiler 200 for matching parameter values to thecorrect item.

The item identification proceeds as described above in the sectionslabeled Geometric-Parameter Matching and Product Identification. In theexample of a retail sales environment, once the product is identified,the item identification processor 300 transfers the productidentification data D233 to a point of sale (POS) system 400.Alternative uses for the system are contemplated other than in forwardlogistics retail systems and processes. For instance, the system couldbe employed in reverse logistics, where product identifications are sentto an auctioneer, a distribution center, a manufacturer, or otherentity.

Housekeeping Functions

In an embodiment, a configuration and monitoring process keeps track ofand updates system calibration data while continually monitoring theactivity of each software process. Each process can be configured toissue a regular heartbeat signal. If the heartbeat from a particularparameter processor or subsystem is not received after a period of time,the configuration and monitoring process can kill and restart thatparticular parameter processor. In embodiments employing an asynchronousdataflow architecture, killing and restarting any one process does notgenerally affect any other process or require re-synchronizing with aclock signal. However, some items passing through the system during there-boot might not be identified, in which case they may be handled bythe normal exception procedures.

File Transfer Process

The file transfer process is responsible for moving lower-priority,generally large, data files across the network from the variousparameter sensors to the history database 350, when this optionaldatabase is included. The file transfer process manages the transfer oflarge files including, but not limited to, the line-scan images producedas part of the indicia reader processing, the height profiles generatedby the dimension estimator, and weight transducer data streams. If filetransfers took place indiscriminately, high-priority, real-time datatransfers such as line-scan data streaming could be interrupted bylower-priority data transfers. The file transfer process manages thosepotential conflicts.

In an embodiment, each real-time file transfer process, which is usedfor large, low-priority (LLP) data sets/files, first stores the LLP datalocally on the hard drive of the parameter processor where the data setsare created. On a regular basis, approximately every three hundredmilliseconds, the file transfer process running on the one or morecomputers hosting that parameter processor checks for newly-depositedLLP data and sends the data over the network to the history database,which may be associated with the item identification processor forconvenience. Data is transmitted in a metered fashion, with limitedpacket sizes and enforced packet-to-packet transmission delays, soaverage network bandwidth is minimally reduced.

The configuration parameters for the file transfer process reside in aconfiguration database. Configuration information such as packet sizes,transmission delays, and IP and destination server addresses are savedin the database. The file transfer process uses standard file transferprotocol, and is implemented in an embodiment using the cURL open-sourcelibrary.

Indicia Reader 130

FIG. 10 is an information flow diagram for an embodiment of the indiciareader. In an embodiment of the system 25, there are eleven line-scancameras, and as previously noted, there is one (virtual) indicia reader130 logically associated with each line-scan camera, even though all ofthe indicia reader processing in practice may occur on the same physicalprocessor. The indicia reader 130 performs three functions: identifyingand decoding any captured indicia and, optionally, extracting indiciaimages from the continuous strip image collected by the line-scan camera132. Thus, each indicia reader 130 in the embodiment effectivelyoperates as a bar code decoder. In the embodiment, the eleven indiciasensors together define a four pi steradian indicia reading system. Eachindicia reader 130 comprises a parameter processor programmed toidentify indicia in the line-scan data captured by each of the line-scancameras 132 and to interpret the indicia into digital indicia data. Aspreviously described, each line-scan camera 132 receives a line-scantrigger D142 based on the motion of the transport system.

A line-scan datum is the output from a single field of a line-scancamera array 131. Each line-scan datum D181 collected by the line-scancamera array 131 is transferred to a line-scan camera buffer 133, whichis internal to line-scan camera 132. The line-scan camera buffer 133compiles the line-scan data D181 together into packages of two hundredline-scan data, which may be referred to as image swaths D237.

In an embodiment, the nominal imaging resolution at the item for each4,096 pixel line-scan camera 132 is approximately two hundred dpi. Thus,an image swath of two hundred line-scan data corresponds to anapproximately one inch by twenty inch field-of-view. Each line-scancamera may be configured to transfer individual image swaths from thecamera to a circular acquisition buffer 135 in the indicia parameterprocessor 134. It should be noted that image swaths D237 are used totransfer data between the line-scan camera 132 and the indicia parameterprocessor 134 for communication efficiency only; the data processing inindicia parameter processor 134 is performed on a line-by-line basis.Further, it should be noted that line-scan camera buffer 133 collectsand saves line-scan data every time the transport system has moved bythe defined trigger increment, independent of the presence of an theitem in the sensing volume.

As discussed above, each image swath D237 is tagged with a relevanttransport system location D148 value, where, generally, one locationvalue is all that is needed for each 200 line swath. Image swaths D237are concatenated in the circular acquisition buffer 135 to re-form theiroriginal, continuous strip image format. Consequently, even if an itemor an indicium on an item spans multiple image swaths D237, the item orthe indicium can be processed in its entirety after additional imageswaths D237 are received by the circular acquisition buffer 135. In anembodiment, the circular acquisition buffer 135 is configured to hold20,000 lines of camera data.

Indicia reader 130 extracts data from buffer 135 and examines line-scandata D181 line by line, in a signature analysis process 136, in both the“cross-track” (within each line) and the “along track” (one line to thenext) directions, to find the signature characteristics of apredetermined indicia format. For example, UPC bar codes can berecognized by their high-low-high intensity transitions. Duringsignature analysis 136, identified indicia are extracted from theline-scan data and the extracted indicia D158 transferred to a decodinglogic process 137. Decoding logic process 137 converts image data into amachine-readable digital indicia value D159. OMNIPLANAR® software(trademark registered to Metrologic Instruments, Inc.; acquired byHoneywell in 2008) is an example of software suitable to perform theindicia identification and decoding in the indicia reader. As will beappreciated, multiple parallel or serial logic processes may be employedto allow for redundant identification. In this regard, where a firstapproach to identification and decoding of a code is unsuccessful, asecond approach may prove fruitful.

In an embodiment, items are generally marked with indicia wherein theindicia conform to various pre-determined standards. Examples of indiciacapable of being read by the decoding logic process 137 include but, arenot limited to, the following: EAN-8, EAN-13, UPC-A and UPC-Eone-dimensional bar codes that capture 8-, 12- and 13-digit Global TradeItem Numbers (GTIN).

It will be understood that the indicia reader 130 may operatecontinuously on the line-scan data. In the context of a bar code reader,when a high-low pattern is observed in the line scan the softwareattempts to identify it as an indicium. If it is identified as such, thesoftware then decodes the full indicium into a digital indicia value. Inparticular embodiments, the line-scan data presented to the decodinglogic process 137 is monochromatic, so the decoding logic process 137relies on lighting and other aspects of the optical configuration in theline-scan data to present information with sufficient contrast andresolution to enable decoding indicia printed according to UPC/EANstandards.

The output from decoding logic process 137 contains three data: thedigital indicia value D159, the transport system location D148corresponding to the one or more line-scan data in which the indicia wasidentified, and the indicia location in camera-centric coordinates D236.In this regard, the camera-centric coordinates could describe a twodimensional area occupied by the entire indicium. Alternately, aparticular X-Y location, for example a centroid of the indicium image, aparticular corner, or an edge, could be assigned to that indicium.

Besides identifying and decoding indicia, a second, optional, functionof the indicia reader 130 is to extract images of individual items asrequested by the item description compiler 200, and to transfer theseimages, the extracted image subframes D234, to the history database 350.The item description compiler 200 issues an image retrieval requestD234, along with the transport system location describing where the itembearing the indicia was located in the field of view of the line-scancamera 132, causing a region extract process 138 to send out the imageretrieval request D149 to retrieve the appropriate subframe D234 fromthe circular acquisition buffer 135. Region extract process 138 thenperforms JPEG compression of the extracted subframe D234, and transmitsit via the file transfer process to history database 350.

Item Isolator 140 and Dimension Sensor 150

Turning to FIG. 11, an information flow diagram of an embodiment of thedimension sensor 150 and the item isolator 140 is provided. Thedimension sensor 150 functions primarily for item dimensioning, ormeasuring the spatial extent of individual items, while the itemisolator 140 functions primarily for item isolation, or sorting out ordistinguishing the items entering the sensing volume. For example, iftwo boxes enter the sensing volume in close proximity, the item isolator140 informs the rest of the system that there are two items to identify,and the dimension sensor 150 informs the system of the size,orientation, and location of each of the two items. As has beenmentioned, these two processes operate in close coordination althoughthey are performing distinctly different functions. Since thedimensioning process actually starts prior to the item being fullyidentified by the item isolator 140, the dimension sensor 150 will beaddressed before the item isolator 140. In an embodiment, both thedimension sensor 150 and the item isolator 140 utilize the output of oneof the line-scan cameras 132A and the area camera 152.

Dimension Sensor 150

In an embodiment, dimension sensor 150 includes the area camera 152 andupward-looking line-scan camera 132A. The dimension estimator 154 (theparameter processor portion of dimension sensor 150) receives data fromarea camera 152, upward-looking line-scan camera 132A, and transportsystem location sensor 120 (shown in FIG. 8).

The main function of dimension sensor 150 is item dimensioning. Duringthe height profile cross-section extraction process 153 and theaggregation process 155, the dimension sensor 150 combines multipleframes from area camera 152 to estimate the locus of points that formthe surfaces of each item using a triangulation process. As implementedin one embodiment, a laser line generator continuously projects a lineof light onto sensing volume conveyor belt (and any item thereon). Theline is projected from above and runs substantially perpendicular to thebelt's along-track direction. In operation, the line of light will runup and over any item on the belt that passes through its field of view.Triggered by the area camera trigger D151, area camera 152 records animage of the line of light. There is a known, fixed angle between thelaser line generator projection axis and the area camera's optical axisso the image of the line of light in area camera 152 will be displacedperpendicular to the length of the line by an amount proportional to theheight of the laser line above the reference surface, which mayconveniently be defined as the upper surface of the conveyor belt. Thatis, each frame from area camera 152 is a line of light, apparentlyrunning from one edge of the belt to the other, with wiggles or sidewayssteps, the wiggles and steps indicative of a single height profile ofthe items on the belt.

Triggered by the area camera trigger D151, the area camera 152 providesan area camera image datum (a single image) every time the transportsensing volume conveyor belt moves by the selected count interval. Insome embodiments the contrast of this height profile may be enhancedthrough the use of an infrared laser and a band pass filter selected topreferentially pass infrared light positioned in front of area camera152. With the filter in place, the output of the area camera 152 is areacamera image data D46, which contains a two-dimensional image showingonly the displacement of the laser stripe as it passes over the item.

The area camera 152 takes snapshots of the laser stripe that isprojected across the sensing volume conveyor belt (edge to edge) by thelaser stripe generator. The area camera image data D46 and the transportsystem location D148 value when the area camera image data D46 wasrecorded, are distributed to item isolating parameter processor 144 anddimension estimator 154, which operate in close coordination.

A height profile cross-section extraction process 153 extracts a heightprofile cross-section D257 from the area camera image data D46 bydetermining the lateral displacement of the laser stripe, which wasprojected by the laser line generator over the item. When there is anangle between the laser stripe projection direction and the viewingangle of area camera 152, the image of the stripe is displaced laterallywhenever the stripe is intercepted by a non-zero height item. Thedimension estimator 154 uses a triangulation algorithm to calculateheight profile cross-section D257 of the item along the original(undisplaced) path of that linear stripe. Note that the height profilecross-section D257 is a height map of everything on the belt at thelocations under the laser stripe.

Height profile cross-section D257 is represented by a collection ofheight data points, which are herein referred to as hixels. Each hixelrepresents the height (z) of a point in an (x,y) position grid. As shownin FIG. 3A, the y-coordinate represents the cross-belt position, thex-coordinate represents the along-belt position, and the z-coordinaterepresents height. Height profile cross-section extraction process 153is applied to each frame of area camera 152, the camera being triggeredeach time the transport system moves by a predetermined distance, about0.005 inches in one embodiment.

The resulting sequence of height profile cross-sections are combinedinto groups by an aggregation process 155 to build closed heightprofiles D247. The aggregation process 155 is based on a pre-definedminimum association distance. If the distance between any two hixels isless than this association distance, they are considered to belong tothe same group. A closed height profile D247 is created once there areno more hixels arriving from height profile cross-section extractionprocess 153 that can plausibly be associated with the group. In otherwords, a closed height profile D247 comprises all of the non-zero heightpoints on the belt that could plausibly be part of a single item. Itshould be noted that a closed height profile D247 may actually comprisetwo or more close together items.

Each closed height profile D247 is compared to pre-determined minimumlength and width dimensions to ensure that it represents a real item anda not just a few, noise-generated hixels. When available, closed heightprofiles D247 are sent to the dimension parameter estimation process 157and the dimension merging process 145. Closed height profiles D247 areoptionally sent to history database 350.

In an embodiment, the height profile may be smoothed to account forsensor noise. In this approach, once a height profile is assembled for asingle object, portions of the profile that appear to be outliers may beremoved. As will be appreciated, removal of apparent outliers prior toprofile assembly could eliminate portions of an actual object that areseparated by a discontinuity, for example a mug handle may appear as anobject separate from the mug body in a particular viewing plane.However, once the profile is assembled, this type of discontinuity wouldtend to be resolved, allowing for smoothing to be performed withoutdestroying information about discontinuous object regions.

It may also be useful to include a zeroing or belt-floor determinationfunction for the height profiling system. During ordinary use, the beltwill continuously pass through the laser stripe projection, and thesystem should measure a zero object height. In theory, the belt floormay be measured using a running average height measurement, and thatmeasurement may be used as a dynamic threshold that is subtracted fromor added to the measured height of objects passing along the conveyor.In practice, it may be difficult to distinguish an empty belt from abelt carrying short items, which could throw off the zero measurement iftreated as an empty belt. One solution is to use a predetermined heightthreshold and for the system to treat anything less than the thresholdheight is an empty belt. Even if a real object passes through thesystem, its effects will be smoothed as a result of the runningaveraging. This may allow for removal of slow-varying portions of thesignal while allowing for removal of high frequency information.

The second data source for dimension sensor 150 is a selected line-scancamera 132A (where the suffix “A” indicates the selected camera),wherein the selected camera is, in this example, specifically theupward-looking line-scan camera array 131A. Camera 132A producesline-scan data after receiving line-scan trigger signals D142. Theline-scan data is then sent to a line-scan camera buffer 133A, asdescribed above for indicia reader 130.

As has already been mentioned, many of the same data processingfunctions are used for dimensioning and item isolation. Thus, theline-scan camera buffer 133A outputs image swaths to the circularacquisition buffer 135A, which is illustrated in FIG. 11 as beingdisposed in item isolator parameter processor 144. Also, as one of skillin the art will recognize, the various data processing steps illustratedherein are grouped as belonging to a particular processor (e.g., itemisolating parameter processor, dimension estimator, etc.) forconvenience of explication only and such grouping is not intended toindicate in which physical processing unit such processing steps occur.

The upward looking line-scan camera is disposed to observe the bottom ofitems on the sensing volume conveyor belt. This camera is aligned toimage through the small gap between the in-feed conveyor belt and thesensing volume conveyor belt. Unlike the other line-scan cameras, theupward looking line-scan camera does not need a large depth-of-focusbecause it is generally observing a consistent plane. That is, thebottom of every item tends to be approximately in the plane of thesensing volume conveyor belt. In general, each line scan comprises somedark pixels (where no item is over the gap) and some illuminated pixels(where part of an item is over the gap). The silhouette generator 141,in the item isolator parameter processor 144 processes the line-scandata D181 received from the circular acquisition buffer 135Aline-by-line and determines if the intensity of any of the pixels exceeda predetermined threshold. Pixels that exceed the threshold are set tothe binary level of high while those below the threshold are set tobinary low, viz., 0. Any line containing at least one high value iscalled a silhouette D242. (A line without one high value is a nullsilhouette.) It will be understood that any silhouette may containinformation about multiple items. The silhouette D242 produced bysilhouette generator 141 is sent to an outline generator 143, which isthe logical process for building bottom outlines.

In conjunction with the upward looking line-scan camera, the lightcurtain assembly also observes the gap 36 and objects passing over it.As described above, pair-wise scans of the LEDs and photodiodes detectshadowed portions of the scanned line. Because the light curtain is abright field detector, its silhouettes correspond not to bright pixels,as in the upward looking line-scan camera, but rather to dark pixels.For many objects, both detectors will mark the same silhouettepositions. However for certain objects, one of the two detectors mayfail to observe the item. For example, the light curtain may fail when atransparent object passes through its field of view, while the cameramay fail when confronted with an object that is a poor reflector. In oneembodiment, the two silhouettes can be subjected to a Boolean ORoperation so that if either or both detectors identify an object, theobject is noted by the system. Alternately, the two systems can operateindependently, and each produce its own set of parameters for evaluationby the system.

The sequence of silhouettes are combined into clusters by an aggregationprocess similar to the generation of groups that takes place in outlinegenerator 143. The outline generator 143 is based on a defined minimumassociation distance. If the distance between any two high pixels in thesequence of silhouettes is less than this association distance, they areconsidered to belong to the same cluster. Thus, a cluster includes bothpixels along a scan line and pixels in adjacent scan lines. The bottomoutline D244 of each such pixel cluster is computed by taking slicesalong the x- (along-belt) and y- (cross-belt) directions, and by findingthe first and last transitions between cluster pixels and background foreach row and column. That is, if there are gaps between cluster pixelsalong a row or column the processor skips these transitions becausethere are more pixels in the same cluster further along the row orcolumn. This bottom outline definition assumes that items are generallyconvex. When this approach to extracting outlines is used, holes insideitems will be ignored. The bottom outline D244 is used during thedimension merging process 145. For a system incorporating both a lightcurtain and a line scan camera, there may be two bottom outlines D244,or alternately, the two acquired data sets can be used in tandem todefine a single bottom outline D244. For the purposes of the followingdiscussion and associated Figures, either outline separately or bothtogether are referred to as D244, and the singular should be understoodas comprehending the plural.

The bottom outline D244 is used in some embodiments to refine thedimension understanding of each item. For example, as described above,the laser stripe viewed by area camera 152 is at an angle to the sensingvolume. Because of the angle, tall items may shadow adjacent shortitems. Information from the upward looking line-scan camera may allowthe dimensioner and item isolator to more reliably detect those shadoweditems and report their bottom outlines in the x and y dimensions.

Before calculating length, width, and height of the smallest boundingbox enclosing an item during the dimension parameter estimation process157, the closed height profile D247 may be mathematically rotated (inthe plane of the conveyor belt) to a standard orientation during thedimension merging process 145. In some embodiments, the closed heightprofile D247 is projected on the x-y plane (i.e., the conveyor beltplane) to correlate with the set of transverse, longitudinal, androtational co-ordinates of the bottom outline D244. The first and secondmoments of these points are calculated, from which the orientation ofthe major and minor axes are derived. The closed height profile D247 maythen be mathematically rotated such that those axes are aligned withrespect to the rows and columns of a temporary image buffer, therebysimplifying calculations of the item's length and width.

The item's length may be defined as the largest of the two dimensions inthe x-y plane while the width is defined as the smaller. The item'sheight is also calculated by histogramming all the item's height datafrom the closed height profile and finding the value near the peak(e.g., the 95th percentile).

For subsequent validation of the item during the dimension mergingprocess 145, additional moments can be computed describing the item'sheight. After rotating the closed height profile D247, thethree-dimensional second moments are calculated. In calculating thesemoments, the item is considered to be of uniform density, filled fromthe top of the measured height to the belt surface. The dimension systemgenerates parameters including, but not limited to, second moments,which are distinct from those used to determine the item's orientation,and the width, length, and height, which are stored in a historydatabase. These parameters, along with the weight information from theweight sensor and the indicia from the indicia reader, are used forvalidating the item.

Once a bottom outline D244 is complete (in the sense that no more pixelswill be associated with this group of pixels), feature extraction isperformed to determine the item's orientation, length, and width. Insome embodiments, pixels along the outline (perimeter) of a cluster onthe x-y plane (i.e., the sensing volume conveyor belt plane) areanalyzed. Pixels within the outline are treated as filled, even if thereare holes within the interior of the actual item. The first and secondmoments of these points are calculated, and the orientations of themajor and minor axes are derived. The bottom outline D244 is thenmathematically rotated such that those axes are aligned with respect tothe rows and columns of a temporary image buffer, simplifyingcalculations of the bottom outline's length and width. The bottomoutline's length, width, orientation, and second moment, collectivelyknown herein as merged data D256, are sent to the item isolation process146 and the dimension parameter estimation process 157.

The bottom outlines D244 and the closed height profiles D247 are alsoused in the dimension parameter estimation process 157. The dimensionparameter estimation process 157 also receives the UII value D231 alongwith the corresponding transport system location D148 regarding an item.

In the dimension parameter estimation process 157, the dimensionestimator 154 receives the bottom outline D244, the UII value D231 withthe transport system location D148, and the closed height profile D247to determine a bounding box for each individual item. In someembodiments, because noise from even a single stray pixel couldadversely change the measurement, an item's length, width, and heightare not based on the maximum extent of the aggregated pixels. Instead,the dimension merging process 145 computes a histogram that bears anumber of pixels in each of the three dimensions, after the item hasbeen rotated to the standard orientation. The distances are computedbetween about the one-percentile and about ninety-nine-percentileboundaries to give the length, width, and height of the item.

If an item does not produce a bottom outline, the only dimensioning dataproduced by the item is a closed height profile. This can occur, forexample, if the bottom of the item is very dark, as perhaps with a jarof grape jelly, though the supplemental use of the light curtain willtend to address this issue. Feature extraction and item isolation areperformed solely on the closed height profile when the closed heightprofile D247 is the only dimensioning data produced. If light curtaindata and closed height profile are available and camera data is not,then those two may be used.

If a group has one or more bottom outlines D244 and one or more closedheight profiles D247, there are several choices for extracting features.In an embodiment, the system may ignore the bottom outlines and onlyoperate on the basis of the closed height profiles. In other words, inthis approach, bottom outlines are only used to assist in theinterpretation of dimensioning data collected from closed heightprofiles. Feature extraction based on multiple closed height profiles isperformed just as it is for a single closed height profile, but usingdata from the group of closed height profiles.

Finally, if the dimension parameter estimation process 157 has notreceived a closed height profile D247 corresponding with transportsystem location value D148, the dimension parameter estimation process157 will have only the bottom outline D244 to determine the dimensioningdata D166 for the item. For example, a greeting card has a height tooshort to be detected by the dimension sensor 150. Therefore, the heightof the item is set to zero, and the item's length and width aredetermined solely from the bottom outline. The length and width arecalculated by rotating and processing the bottom outline's x,y data asdescribed above for the dimension estimator 154 using first and secondmoments. When no closed height profile is available, a three-dimensionalsecond moment is not calculated.

Periodically, the dimension parameter estimation process 157 checks thetransport system location D148, and sends collected dimensioning dataD166 to the item description compiler 200 when it determines that thereare no further closed height profiles D247 or bottom outlines D244 to beassociated with a particular item. The dimension estimator 154 also usesthe data to estimate various dimensioning data D166 including, but notlimited to, parameter values regarding the general shape of the item(cylindrical, rectangular solid, necked bottle shape, etc.), the item'sorientation on the transport system, and details concerning the item'sthree-dimensional co-ordinates on the sensing volume conveyor belt. Inthis embodiment the dimension sensor 150 is also capable of calculatingother parameter values based on the size and shape of the item. Thevarious dimensioning data D166 along with the transport system locationD148 values of the items, are sent to the item description compiler 200as they are calculated.

Item Isolator 140

FIG. 11 also shows the Item Isolator 140, which may allow the system tooperate on non-singulated items. In operation, the item isolator 140recognizes that something (one or more items) has entered the sensingvolume. During the dimension merging process 145, when the closed heightprofiles D247 and bottom outlines D244 overlap spatially (i.e., they areat least partially merged) they may be associated with a single item,and the item isolator 140 may be said to have isolated an item passingthrough the sensing volume. In the item isolation process 146, the itemisolator 140 merges the closed height profile D247 with the bottomoutline D244, generating merged data D256. Due to the way bottom outlineD244 and closed height profile D247 descriptions are created, all bottomoutlines D244 are mutually disjointed spatially, and all closed heightprofiles D247 are mutually disjointed spatially. The dimension mergingprocess 145 waits for an event. The dimension merging process 145 storesand keeps tracks of closed height profiles D247 and bottom outlines D244as they are received. When a new closed height profile D247 is received,the dimension merging process 145 checks it against the collection ofbottom outlines D244 to see if the closed height profile D247 and aparticular bottom outline D244 overlap spatially. Closed height profilesD247 and bottom outlines D244 that overlap spatially are placed into onegroup. The dimension merging process 145 does not check the closedheight profile D247 against other closed height profiles because theyare, by definition, disjoint. Similarly, after a new bottom outline D244is received, it is checked against the collection of the closed heightprofiles D247 received to see if the bottom outline D244 overlaps anyclosed height profile D247.

During the dimension merging process 145, the item isolator 140 matchesthe transport system location D148 values of the bottom outline D244with any closed height profile D247 that shares substantially the sametransport system location D148 values. At this point, the item isolator140 recognizes the bottom silhouette of the item and recognizes theheight of substantially every point of the item, and is ready to deliverthe merged data D256 to the item isolation process 146.

Second, the item isolator 140 determines how many distinct itemscomprise the object that entered the sensing volume. In certain cases,several individual items are mistaken as a single item in one or theother data sets. The purpose of the item isolation process 146 is todetermine when closed height profile D247 and bottom outlines D244represent the same single item and when they represent multiple items.

Third, the item isolator 140, specifically the item indexer, assigns aUnique Item Index value (UII) D231 to each distinct item, and, fourth,along with the UII D231, the item isolator 140 identifies thetwo-dimensional location of the item (the transport system location D148value). With knowledge of the merged data D256, likely belonging to asingle item, the item isolator 140 assigns a UII value D231 to themerged data D256 with known transport system location D148 values. Theitem isolation process 146 results in the UII value D231 along with thetransport system location D148 being communicated to the dimensionparameter estimation process 157 for further processing by the dimensionestimator. The dimension parameter estimation process 157 receives theUII value D231, the merged data D256 with known transport systemlocation D148 values, and outputs the dimensioning data D166 with theUII value D231 (and the transport system location) to other parts of thesystem (particularly the item description compiler 200 as shown in FIGS.8 & 9).

Item isolation process 146 improves the reliability of system output. Inan embodiment, a failure of the item isolator 140 stops all systemoperations, because the system cannot ascertain the number of items inthe sensing volume or the location of those items, and, therefore, doesnot know what to do with the data from the parameter sensors. However,failure of only a portion of the item isolation system need not stop thesystem. The item isolation process 146 allows the item isolator 140 tocontinue to function if the upward looking line-scan camera stopsfunctioning, using light curtain data and/or closed height profiles D247for each item.

Conversely, if the dimension estimator 154 fails and the upward lookingline-scan camera outline detection and/or the light curtain continues tofunction, bottom outlines D244 but no closed height profiles D247 willbe reported. The system may continue to operate in a degraded mode sincethe heights of items are not available for item identification. However,determination of item weight, length, and width is still possible, anditems will not generally go through the sensing volume undetected, evenif a number of exceptions is increased.

Weight Sensor 170

Referring now to FIG. 12, a schematic illustration of weight sensor 170is shown. Weight sensor 170 includes an in-motion scale 172 and a weightgenerator 174. In-motion scale 172 includes object sensors (in-feedconveyor belt object sensor 173A, sensing volume entrance object sensor173B, and sensing volume exit object sensor 173C are shown) and loadcells 175A, 175B, 175C, and 175D.

Object sensors, such as in-feed conveyor belt object sensor 173A,sensing volume entrance object sensor 173B, and sensing volume exitobject sensor 173C, allow the weight generator to track which items areon the in-motion scale 172 at a given time. Sensing volume entranceobject sensor 173B is positioned near the in-feed end of the sensingvolume. Sensing volume exit object sensor 173C, positioned near theout-feed end of the sensing volume, along with sensing volume entranceobject sensor 173B provides loading information to enable the system toaccurately calculate the weight of multiple items in the sensing volumeat a given time. In-feed conveyor belt object sensor 173A is positionedseveral inches upstream from the in-feed end of the sensing volumeconveyor belt and enables an optional operating mode in which thein-feed conveyor belt can be stopped.

To put it another way, the inclusion of object sensors enables thesystem to estimate the weight of most of the individual items bycombining the instantaneous total weight on the sensing volume conveyorbelt (not shown in FIG. 12) with the item's transport system locationD148 values. However, in some embodiments, accurate weight data D191cannot be measured by the weight generator 174 when items enter thesensing volume while other items are exiting. Therefore, in theseembodiments, object sensors may be employed to prevent simultaneousloading and unloading of items from in-motion scale 172. In other words,object position logic 176, upon receiving transport system location D148and data from in-feed conveyor belt object sensor 173A, sensing volumeentrance object sensor 1738, and sensing volume exit object sensor 173C,can determine that an item will be entering the sensing volume at thesame time that an item will be exiting the sensing volume and can signalthe transport system to hold back from passing any new items to thesensing volume if there is an item about to depart from the sensingvolume. In other embodiments the object position logic can also stop thesensing volume conveyor belt if, for example, the scale has not had timeto settle after loading a new item. The object position logic 176transmits start and stop signals D115 to the average and differencingprocess 178 where the logic calculates the average of and the changes ininitial sensing data received from load cells 175 to ensure thatcalculations are performed at the proper time.

It will be noted that stopping and starting the conveyor belts to holdback items from loading into/unloading from the sensing volume has nonegative effects on the measurements made by the system; from theperspective of the sensing volume stopping the in-feed conveyor beltonly spreads out items on the sensing volume conveyor belt whilestopping the sensing volume conveyor belt puts all of the digitalprocessing steps into a suspended mode that may be restarted when thebelt is restarted.

As shown in FIG. 12, object position logic 176 additionally uses theinformation received from the object sensors along with the transportsystem location D148 to issue belt control commands D50. These commandsare sent to the transport system location sensor 120 (FIG. 9) wherein,in one embodiment, the motor controllers reside. For example, using theinformation received from sensing volume object sensor 173C, objectposition logic 176 can determine that an item is about to exit thesensing volume. In order to prevent an item from entering the sensingvolume at the same time, object position logic 176 can send a beltcontrol command D50 to stop the in-feed conveyor belt from continuing totransport items toward the sensing volume. Additionally, oralternatively, belt control commands D50 can include increasing ordecreasing the speed of the conveyor belts in order to limit the numberof items that an operator of the system 25 can physically place on thein-feed conveyor belt. Similarly, in some embodiments, the in-motionscale 172 may require periodic self-calibration time during which noitems are permitted on the scan tunnel conveyor belt, allowing it toreturn to its tare weight in order to maintain accuracy. Thiscalibration condition is achieved by stopping the in-feed conveyor belt.Other belt control commands D50 can be transmitted by object positionlogic 176, depending on the specific application contemplated.

Load cells 175A, 175B, 175C, and 175D are disposed in the load path andtypically support the sensing volume conveyor belt (not shown in FIG.12, but shown in at least FIG. 2B). Each load cell generates anelectrical signal proportional to the compression force applied to theload cell. In some embodiments, load cells 175A, 175B, 175C, and 175Dare digitized with a high sample rate (e.g., 4000 samples per second)before being transmitted for processing by weight generator 174.

The high sample rate load cell samples are received by the summationprocess 177, wherein the signals from the load cells are summed andscaled to represent the total weight data of the in-motion scale 172 andany items on the in-motion scale 172. The total weight data D190 fromthe summation process 177 is optionally sent to the history database instep D190. Additionally, this sum is low-pass filtered (or averaged) toimprove the signal-to-noise ratio and give a more accurate total weightin the average-and-differencing process 178. The number of digitalsamples included in the average calculated during theaverage-and-differencing process 178 is limited by the number of samplestaken while the weight on the in-motion scale 172 is stable. Forexample, if only one item were loaded onto the sensing volume conveyorbelt, the stable period extends from the moment the one item is fully onthe sensing volume conveyor belt until the moment the item begins tomove off of the sensing volume conveyor belt. When more than one item ison the sensing volume conveyor belt at a given time the stable periodsare limited to the times when no item is being loaded onto or moving offof the sensing volume conveyor belt. In a noise-free environment, theweight generator could identify stable periods by the data alone.However, the weight generator typically operates in the presence ofsome, if not a significant amount of, noise. Object sensors 173A, 173B,and 173C, therefore, inform the weight generator (via object positionlogic 176) when items are loading or unloading from the sensing volumeconveyor belt for appropriate averaging. It should be noted thatalthough the language herein suggests temporal considerations, in anembodiment the system process does not include a clock signal, butrather is only clocked by incremental movements of the scan tunnelconveyor belt. Thus, a stable period can be extended by stopping thescan tunnel conveyor belt and the actual number of samples in theaverage will continue to increase at the data sample rate (4000 samplesper second in one embodiment).

Additionally, average-and-differencing process 178, as commanded by thestart and stop signals D115, performs a differencing operation betweenweight values obtained before an item is loaded onto/unloaded from scale172 and after an item is loaded onto/unloaded from scale 172. The weightvalues thusly obtained are assigned to the item or items loadedonto/unloaded from scale 172 during the instant transition. There areseveral alternative approaches to performing the differencing functionthat may be used to achieve essentially the same weight data D191. Theselection among these alternatives is generally determined by theavailable hardware and digital processing resources and by operatingconditions (e.g., load cell signal-to-noise ratio, load cell drift,etc.). One particular approach is discussed below in conjunction withFIG. 13.

Returning to FIG. 12, weight values D191A are transferred fromaverage-and-differencing process 178 to an assign-weight process 179,wherein weight values D191A are combined with object position data D113,which is data that was generated by object position logic 176. It shouldbe noted that object position logic 176 cannot identify individual itemsin an overlap condition. Object positions D113 are determined bycombining the off and on signals from the object sensors with thetransport system locations D148. The combination of item weights andobject positions are the item weight data D191. For non-overlapped itemsthe item weight data is the weight of the item; for overlapped items theitem weight data is the combined weight of the more than one item. Itemweight data D191 is passed on to the item description compiler 200.Optionally, the continuous stream of total weight data D190 is sent tothe history database 350 (as shown in FIG. 8).

As mentioned above, various approaches are available to calculate theweight of individual items on scale 172. FIG. 13 provides timingdiagrams depicting schematically each output from an element of anembodiment of the weight sensor 170 that is schematically illustrated inFIG. 12. The first data line at the top of FIG. 13 provides an exampleof an output of summation process 177. The second data line of FIG. 13provides an example of an output of the in-feed conveyor belt objectsensor 173A. The third data line of FIG. 13 provides an example of anoutput of the sensing volume entrance object sensor 173B. The fourthdata line of FIG. 13 provides an example of an output of the sensingvolume exit object sensor 173C. The first data line of FIG. 13illustrates the changing, summed, digitized load cell signals as afunction of time, where constant transport system speed is assumed. Thesecond, third and fourth data lines of FIG. 13 show the (binary) outputof the three object sensors.

In the second data line of FIG. 13, item A is shown detected first bythe in-feed conveyor belt object sensor 173A, at the third to fourthtime interval. While item A remains on the in-feed conveyor belt (asshown detected by in-feed conveyor belt object sensor 173A), the firstdata line shows that the weight sensor 170 does not detect a weightvalue as shown by the constant (0,0) from the start of the clock at zeroto the fifth time interval. As item A enters the sensing volume conveyorbelt shown in the third data line from the fifth second to the sixthtime interval, the sensing volume entrance object sensor 173B detectsthe presence of item A. Item A's weight is recorded by the weightgenerator, as shown from about point (5,0) to about point (6,3) on thefirst data line in FIG. 13. After item A has completely crossed the beltgap and is entirely located on the sensing volume conveyor belt, theweight sensor 170 shows the weight of item A as static, from about point(6,3) to about point (11.5, 3). Cued by item position logic 176, theaverage-and-differencing process 178 averages load cell signals duringthe first indicated acceptable averaging window and takes the differencebetween the weight value 3, obtained at the end of said first acceptableaveraging window, and the weight value 0, obtained just prior to item Aloading onto the scale (as indicated by object sensors 173A and 173B).

As shown in the second data line, from the nine and half time intervalafter the start of the system to nearly the eleventh time interval, thein-feed conveyor belt object sensor 173A detects the presence of anotheritem, B, on the in-feed conveyor belt. As item B enters the sensingvolume on sensing volume conveyor belt, sensing volume entrance objectsensor 173B detects item B's presence from about the 11.5 to about the13.5 on the x axis time interval. The total weight of item A and item Bis recorded by the weight sensor 170, as shown from about point (11.5,3) to point about (13.5, 9) on the first data line. After item B hascompletely crossed the belt gap and is entirely located on the sensingvolume conveyor belt, the total weight of item A and item B is static,from about point (13.5, 9) to about point (20, 9). Cued by objectposition logic 176, the average-and-differencing process 178 averagesload cell signals during the second indicated acceptable averagingwindow and takes the difference between the weight value 9, obtained atthe end of said second acceptable averaging window, and the weight value3, obtained previously for item A. That is, since the weight sensor 170knows that item A weighs about three units, and the aggregate weight ofitem A and item B is nine units, then the system calculates that item Bweighs about six units.

As shown in the fourth data line of FIG. 13, from the twentieth timeinterval to the twenty-first time interval after the start of thesystem, the sensing volume exit object sensor 173C detects the presenceof item A exiting the sensing volume on the sensing volume conveyorbelt. As item A leaves the sensing volume on the out-feed conveyor belt,the weight sensor 170 detects a diminishing weight value from aboutpoint (20, 9) to about point (21, 6). The weight sensor 170 can thusverify the weight of item A. Since the weight value dropped from aboutnine units to about six units when item A left the sensing volume, itemA weighs about 3 units.

After item A has completely traveled out of the sensing volume and isentirely located on the out-feed conveyor belt, the weight sensor 170shows the weight of item B as static, from about point (21, 6) to aboutpoint (27, 6). Again the weight sensor 170 can verify its firstcalculation of the weight value for item B by detecting a static weightvalue of about six units during the period of time that only item B isdetected on the sensing volume conveyor belt. As shown in the fourthlinear graph, from the twenty-seventh time interval to the twenty-ninthtime interval after the start of the system, the sensing volume exitobject sensor 173C detects the presence of item B exiting the sensingvolume on the sensing volume conveyor belt. As item B leaves the sensingvolume on the out-feed conveyor belt, the weight sensor 170 detects adiminishing weight value from about point (27, 6) to about point (29,0). Subtracting 6 from 0 verifies that the item that just left thesensing volume (item B) weighs 6 units.

Load cell weight sensors often exhibit zero offset drifts over time andtemperature variations. This potential drift is shown schematically inthe first data line of FIG. 13 for time intervals beyond 29. In oneembodiment of the system, this drift is reset automatically duringperiods in which no items are on the scale, as cued by object positionlogic 176.

The calculation approach described above may fail to operate properlywhen one item is loaded onto the scale at the same time that a seconditem is unloaded. To avoid this condition, in one embodiment objectposition logic 176, an AND condition for in-feed conveyor belt objectsensor 173A and sensing volume exit object sensor 173C generates acommand to stop the in-feed conveyor belt until the exiting item hascleared the sensing volume. This belt motor control command D50 may betransmitted to transport sensor processor 127 (FIG. 9), where the motorcontrollers reside for convenience.

As has been mentioned, there are multiple alternative approaches toprocess the total weight signals D190 to estimate the weight ofindividual items when they are non-singulated on the scale, generallyincluding making weight estimates before, during, and/or after each itementers and/or leaves the scale. In addition there are alternativeapproaches that, under certain operating conditions, can estimate theweight of individual items even if they are partially overlapped. Forexample, consider the total weight values illustrated in the first dataline of FIG. 13. The slopes of the transition lines between theacceptable averaging windows are proportional to the weights of theitems loading onto or unloading from the scale. When there are twopartially overlapping items loading onto the scale, the slope of thetransition line changes as the number of items being loaded changes.Thus, in a noise free environment it is a trivial exercise to apportionthe total weight measured during the stable period to the twooverlapping items that loaded onto the scale.

The Geometric Merging Process Occurring within Item Description Compiler200

FIG. 14 is a data flow diagram for an item description compiler 200conducting the geometric merging process. The item description compiler200 aggregates the parameter values corresponding to an individual iteminto an item description, wherein the parameter values are received fromthe various parameter processors. In the embodiment depicted in FIG. 14,the parameter values are shown as the UII value D231, dimensioning dataD166, weight data D191, and digital indicia data D235, but otherparameter values are contemplated herein. Each parameter value, aspresented to the description compiler includes its correspondingtransport system location values D148. The item description compiler 200uses these location values to match parameter values that apply to asingle item. That set of matched parameter values is the itemdescription. The item description, when judged to be complete by theitem description compiler 200, is then provided to the productidentification processor.

The item description compiler 200 uses a geometric-based dataassociation technique, using the object association library describedabove to aggregate the asynchronously produced item parameter values.Time can be used to correlate the various parameter values with a uniqueitem but, because the various parameter values may have been produced atdifferent times as the item moved through the scan tunnel, and becausebelt velocity may not be constant, this approach can be difficult toimplement. However, the transport system location at which each item isdisposed is a fixed parameter associated with that one item (once itenters the scan tunnel), as is the transport system location value,relative to a known reference location at which each sensor makes itsmeasurement. Therefore, each measured parameter value can be matched tothe item that was at the sensor's location at the moment of measurement.

During system operation, the transport location sensor 120 (shown inFIG. 9) is continually supplying a transport system location value toeach parameter processor. Each parameter processor tags the parametervalues it produces with the transport system location valuecorresponding to the instant its initial sensing data was collected.Additionally, item isolator 140 and dimension sensor 150 (both shown inFIGS. 9 & 11) provide a full three-dimensional location for eachisolated item, meaning that they provide the item description compiler200 with the mathematical description of where the surfaces of each itemare in camera space. The library of calibration data 250 is a record ofwhere in physical space each sensing element in each parameter sensor isaimed. The transformation process 202 converts the mathematicaldescription of the surfaces of each item from camera space to physicalspace with accurate spatial (x,y,z) positioning information.

The transformation process 202 uses detailed knowledge of each parametersensor's three-dimensional field of view (e.g., the vector describingwhere each pixel on each line-scan camera is pointed inthree-dimensional space). With that information, the item descriptioncompiler 200 can associate data from the multiple parameter sensors withthe item that was at a particular transport system location, as long asthe spatial uncertainty of each measurement coordinate can be keptsufficiently small. In an embodiment, all spatial measurements are knownto accuracies generally less than about two-tenths of an inch. Thesmallest features requiring spatial association are the indicia, whichin practice measure at least about six tenths of an inch in theirsmallest dimension even with minimum line widths smaller than the aboutten mils specified by the GS1 standard. Consequently, even the smallestindicia can be uniquely associated with the spatial accuracies of theembodiment described.

The first step in being able to spatially associate parameter valueswith a particular item is to calibrate the absolute spatial positions ofeach parameter sensor's measurements. For example, the left-frontline-scan camera's indicia reader transmits each digital indicia value,along with the line scan camera's pixel number of the center of theindicia and the transport system location value D148 at which the camerawas triggered when reading the first corner of the indicia. The itemdescription compiler receives that information and transforms the pixelnumber and transport system location into absolute spatial co-ordinates.

For the indicia reader, pixels corresponding to the four extreme pointsdefining the edges of the visible plane inside the sensing volume areidentified by accurately positioning two image targets, one at each endof a given camera (at the extreme ends of the sensing volume), and asclose to the line-scan camera as possible, within the sensing volume.The pixels imaging those targets define the two near-end points of thevisible image plane. The process is repeated for the two extreme pointsat the far-end of each line-scan camera's field of view.

For example, for the side line-scan cameras, targets are placed justabove the sensing tunnel conveyor belt and at the maximum item height,as close to the input mirror as possible inside the sensing volume. Thesame targets are imaged at the far end of that line-scan camera's range.The (x,y,z) co-ordinates for each test image target are recorded, alongwith the particular camera and camera pixel number where the image ofeach target appears. The three co-ordinates define the imaging plane forthat camera. Through interpolation or extrapolation, the imaging ray forany pixel comprising that line-scan camera can be derived from thosefour points, and that line-scan camera's reported three co-ordinates ofwhere it saw an indicium with the optical ray along which it was imagedcan be mapped.

Accurate spatial (x,y,z) positioning information is known for each imagetarget during geometric calibration. In some embodiments, the coordinatesystem is as illustrated in FIGS. 3A and 3B. The geometric calibrationis performed manually, without making use of data from the transportlocation sensor, although the dimension estimator uses that data for itsown processing. However, automated geometric calibration is alsopossible, using data from the transport location sensor. In anembodiment, the geometric calibration data is stored in a library 250.However, it should be clear that geometric calibration data D201 is nota required element in all embodiments. In those embodiments where it ispresent, the geometric calibration data D201 is transferred from thelibrary 250 to the transformation process 202 within the itemdescription compiler 200.

Although the line-scan camera ray alone does not uniquely define theexact point in space where the indicium was located, the line-scancamera ray intersects the three-dimensional representation of the itemitself, as provided by the item isolator 140 and dimension estimator150. Together, the line-scan camera rays and the three-dimensional itemrepresentations create a one-to-one correspondence between indicia anditems.

Another parameter sensor using a level of geometric calibration is theweight estimator. In the described embodiment, the weight estimatorobtains item X-axis position information from its object sensors. Thatis, in terms of FIG. 14, the weight estimator assigns a weight value toitem A or B based on the output of at least the sensing volume entranceobject sensor, which indicated where along the virtual belt the itemswere first loaded onto the scale. The object sensor positions can bemanually calibrated by simply measuring their distances relative to thedimension estimator co-ordinates, or automatically calibrated usingmoving calibration items and instantaneous transport system locationsreported by the transport location sensor.

It will be noted that in the illustrated embodiment items are loadedonto the in-motion scale 172 before they are observed by area camera152. Similarly, the upward looking line-scan camera 88 (shown at leaston FIG. 4A) might read an item's indicium before it is observed by areacamera 152. Thus, weight measurements and indicia readings may be madebefore the dimension sensor 150 and item isolator 140 (schematicallyshown in FIG. 11) have determined what items are in the scan tunnel.Indeed, the system's product identification function would perform aswell with dimension sensor 150 and upward-looking line scan camera 132Alocated at the end of the scan tunnel as it does with those sensorslocated at the front of the scan tunnel. The frontward location of thesetwo sensors is preferred only to minimize the processing lag required toproduce an identification. That is, the product identification can beproduced sooner after the item leaves then tunnel when the data iscollected at the front of the tunnel than at the end of the tunnel.

The weight estimator only knows the X-axis location of the items itweighs. Two items that overlap side-by-side (i.e., have common Xlocations but different Y locations) on the in-motion scale may bedifficult to weigh individually. Thus, the reported weight in thisinstance is an aggregate weight of all the side-by-side items at thattransport system location (x value). When a weight value arrives at theitem description compiler 200 (shown schematically in FIG. 14) with atransport system location that matches more than one item, the itemdescription compiler 200, in some embodiments, adds that weight value toeach item's item description D167, along with an indication that it isan aggregate weight. In other embodiments, the unique item identifier(s)for the other side-by-side items are also added to the item descriptionD167, for reasons described below.

The various parameter values that are transformed through thetransformation process 202 become spatially-transformed parameter valuesD70, which are then delivered to an information queue 207. Theinformation queue 207 is a random access buffer, that is, it does notoperate in a first in first out system. Because there are generallymultiple items on the sensing volume conveyor belt, and because eachparameter sensor sends its sensed parameters as soon as it recognizesthem, the information queue 207 at any point in time containsspatially-transformed parameter values D70 from multiple items arrangedin their order of arrival. Because, for example, the latency between thetime an item's indicium physically passes through a line-scan camera'sfield-of-view and the time the indicia reader produces the correspondingindicia value is highly variable, it is even possible that somespatially-transformed parameter values D70 may not be recognized orinterpreted until long after the item has exited the system 25.

The item description compiler 200 seeks to determine which of thereported spatially-transformed parameter values D70 in the informationqueue 207 was measured on the surface or at the location of the itemthrough the process of geometric merging or geo-parameter matching.

The data merging process of the item identification processor 300depends on the dimension sensor 150 and the item isolator 140. The itemisolator 140 determines what items are in the sensing volume (and givesthem a unique tracking number, the UII) and the dimension sensor 150creates dimensioning data, including but not limited to the closedheight profiles with the corresponding bottom outlines. Together, thedata from the item isolator 140 and the dimension sensor 150 form thebaseline entry in the item description D167 being created in the itemdescription compiler 200. Other parameter values are identified asbelonging to the item and are added to the item description D167. Insome embodiments, the data merging process 215 receives transport systemlocations D148 and delivers image retrieval requests D149 to the regionextract process 138 of the indicia reader 130 shown in FIG. 10.

As mentioned above, parameter values are received by the itemdescription compiler 200 from the various parameter sensors, undergotransformations 202 and are temporarily placed in an information queue207. As the item description compiler 200 builds an item descriptionD167 through having the data merging process 215 matchspatially-transformed parameter values D70 with the same transportsystem locations D148, it sends a data request D169 to the informationqueue 207 to remove the spatially-transformed parameter value D70 fromthe information queue 207 to place it in the appropriate itemdescription D167. Thus, spatially-transformed parameter values D70 arecontinuously added to and deleted from the information queue 207.

Finally, the item description D167 is sent out to the itemidentification processor 300. The item description compiler 200 sendsthe item description D167 file to item identification processor 300 at apoint in the processing based on one or more selected criteria. Thecriteria may include, for example, sending the item description D167when the current transport system location exceeds the item location bymore than about 25% of the length of the sensing volume. In anembodiment, the send criterion may correspond to a belt position lessthan or equal to a particular distance from the end of the output belt.

Some parameter values are never associated with any item and may bereferred to as orphan values. Orphan values are created if, for example,a parameter value is delayed by a processor reboot or if the transportsystem location D148 value has a defect. Likewise, where an item movesrelative to the conveyor, for example a rolling bottle or can, certainvalues may be orphaned. An accumulation of unmatched parameter values inthe information queue 207 has the tendency to impair system performance.In some embodiments, the item description compiler 200 can includefunctionality for deleting parameter values from the information queue207 over a certain selected time period. The determination to deleteparameter values depends on whether the virtual location of newspatially-transformed parameter value D70 arriving in the informationqueue 207 is significantly beyond the length of the out-feed conveyorbelt, for example. This condition would indicate that the orphan valueis associated with an item long gone from the sensing volume.

Item Identification Processor 300

FIG. 15 is a data flow diagram for the item identification processor300. The item description compiler 200 creates an item description D167for each item isolated by the item isolator. The item identificationprocessor 300 opens a file for each item description D167 provided to itby the item description compiler 200. The item description D167 includesa list of all the available measured parameter values collected by thesystem. The basic function performed by item identification processor300 is to compare item description D167 to a set of productdescriptions, stored in the product description database 310, and todecide according to pre-determined logic rules if the item is one ofthose products. In some embodiments, the product descriptions in productdescription database 310 contain the same sort of information about theproducts as have been collected about the items. Typically, productdescriptions include digital indicia values, weight data, anddimensioning data about the products. In some embodiments, the productdescription may comprise other parameter values of the products,statistical information about the various parameters (for example, thestandard deviation of the weight), digital photographs of each product,etc.

In an embodiment, a polygonal representation of an item can be generatedfor the focal plane space of each camera. Thus, for each object, thereare multiple polygons generated corresponding to each of the cameraviews of that object. By way of example, for a system having sevenperspectives, seven polygons would be generated and stored for use inthe merging process as described below.

The item identification processor 300 attempts to determine a best matchbetween the unknown item's parameter values and the database of (known)product parameters. In some embodiments, the indicia value (typicallythe UPC), is used as the primary database query. Assuming an exactindicia match is found in the product description database, the itemidentification processor 300 examines the remaining parameter values todecide if the item is the product represented by the indicia. This is avalidation that the UPC has not been misread or destroyed. As describedabove, partial UPCs (or other codes) may be further evaluated to narrowa number of choices of possible items, and in an embodiment, a smallnumber of choices can be passed to an operator for resolution.

The item description D167 is provided to a formulate-database-queryprocess 305, which compares available item parameters to determine basedon, for example, a given indicium, weight and height, what the item is.When a query D209 has been formulated, the formulate-database-queryprocess 305 delivers it to the product description database 310, whichin turn provides a query result D210 to a product identification logicprocess 312. Product identification logic 312 compares query resultD210, which is a product description, with the original item descriptionD167 to decide if the two descriptions are similar enough to declare anidentification.

The item identification processor 300 is preprogrammed with a set oflogic rules by which this validation is performed. In some embodiments,the rules are deterministic (for example, the weight must be within x %of the nominal weight for the product). In other embodiments, the rulescan be determined using, for example, fuzzy logic.

Fuzzy or adaptive logic may find particular use in productidentification logic 312 to address unusual situations. For example,some items will have multiple digital indicia values and certainproducts will be known to have multiple visible indicia, since multipleline-scan cameras produce images of each item and since some items havetwo or more distinct indicia (e.g., a multi-pack of water, where eachbottle may have one bar code, and the multi-pack case may have adifferent bar code). In this example, fuzzy logic may perform betterthan a strict rule that governs how conflicting information is handled.

Although in some embodiments the digital indicia value may be apreferred parameter value for the database lookup, there are instancesin which the formulate-database-query process 305 uses one or more ofthe other parameter values in a first attempt to try to identify anitem. For example, where indicia are misread or have been partially orfully obscured from the line-scan camera, the formulate-database-queryprocess 305 is programmable to use the other parameter values previouslydescribed to accurately identify the item as a product. For example, ifthe weight, shape, and size of the item have been measured with a highdegree of certainty and a few of the digits of the bar code were read,these data may provide a sufficiently unique product identification.

The output of product identification logic 312 is either a productdescription with a probability of identification or an exception flagwhich indicates that no matching product description was found. A lackof match may occur, for example, where an item is scanned that had neverbeen entered into the database. This output is transferred to aproduct/exception decision process 314 in which a programmable tolerancelevel is applied. If the probability of identification is above thistolerance, the product identification data D233 and the UII value D231are output. In typical embodiments, the identification output isdelivered to a POS system 400. On the other hand, if the probability ofidentification is below the tolerance level, then product/exceptiondecision process 314 associates an exception flag D232 with the UIID231. Optionally, in some embodiments, when an item is flagged as anexception the UII D231 is delivered to an exception handler 320. Theoptional exception handler 320 can include doing nothing (e.g., lettingthe customer have this item for free), providing an indicator to asystem operator to take action, or it could involve performing anautomatic rescan.

Another optional function that is part of the item identificationprocessor is the ability to update the product description databasebased on the new item's parameter values. For example, the mean andstandard deviation of the weight of the product, which are typicalparameters stored in product description database 310, can be refinedwith the new weight data collected each time that particular product isidentified. In some embodiments, the item identification processor 300updates its product description database 310 with every parameter valueit receives regarding items passing through the sensing volume. Thedatabase update process 313 receives UII D231 and item description D167from the formulate database query 305 process and performs the databaseupdate when it receives the product description D233 and UII D231 fromproduct/exception decision process 314. Database update process 313 alsoreceives notice when UII D231 is an exception (flag D232) so that it canpurge inaccurate product descriptions D167 associated with the exceptionUII D231.

Prior to multi-read disambiguation, the Merger employs a single-pass“best match” algorithm for assigning barcodes to an item at itsscheduled output position (i.e., the Y belt position at which the Mergersends information for an item to the output subsystem for subsequenttransmission to the POS). The best match algorithm for barcodes takes asinput 1) a single item for which output is to be generated, 2) an itemdomain consisting of all items to be considered when identifying thebest barcode-to-item match—the output item is also part of this domain,and 3) a barcode domain consisting of all barcodes available to beassigned to the output item.

The algorithm works by visiting each barcode in the barcode domain, inturn, and computing a matching metric (Figure Of Merit—FOM) between thebarcode and all items in the supplied item domain. Once allbarcode-to-item associations have been computed, the algorithm discardsall associations with FOM values that are below a specific threshold(this threshold may be arrived at heuristically, and may be updated inaccordance with real-world performance, either as a user setting orautomatically). All remaining barcode-to-item associations are thensorted according to distance along the camera ray and the associationwith the shortest distance is considered to be the best match (the logicbeing that it is not likely to read a barcode on an item that is behindanother item—thus, the barcode closest to the camera lens is more likelyto be properly associated with the front item). If the item identifiedas the best match is the same as the output item, the barcode isassigned to the output item. Otherwise, the barcode is not assigned.

While in the foregoing specification this invention has been describedin relation to certain particular embodiments thereof, and many detailshave been set forth for purpose of illustration, it will be apparent tothose skilled in the art that the invention is susceptible to alterationand that certain other details described herein can vary considerablywithout departing from the basic principles of the invention. Inaddition, it should be appreciated that structural features or methodsteps shown or described in any one embodiment herein can be used inother embodiments as well.

1. A system for asynchronously identifying an item within a sensingvolume comprises: a plurality of object sensors, each object sensorconfigured and arranged to determine at least one parameter describingobjects as they are relatively moved with respect to the sensing volume,and having a known position and attitude with respect to the sensingvolume; a position sensor, configured and arranged to produce positioninformation relating to the relative movement, wherein the positioninformation does not comprise system clock information; a processor,configured and arranged to receive the parameters from the objectsensors and to associate the parameters with respective ones of theobjects on the basis of the position information and on the basis of theknown position and attitude of the object sensor that determined eachrespective parameter, without taking into account system clockinformation, and to, for each object having at least one associatedparameter, compare the at least one associated parameter to known itemparameters to assign an item identification to the object.
 2. A systemas in claim 1, wherein the object sensors further comprise: a heightdimensioning sensor comprising a substantially planar light source,configured and arranged to project planar illumination at an angle to apath of the objects during their relative movement in the sensingvolume; an associated height dimensioning detector, constructed andarranged to detect a reflection of the planar illumination; and whereinthe processor is configured and arranged to determine, based on thedetected reflection and the angle, a height profile of each object. 3.(canceled)
 4. A system as in claim 1, further comprising an objectdiscriminator that is configured and arranged to singulate objects basedon object outlines created from a plurality of instantaneous widthsmeasured by the dimensioning sensors.
 5. A system as in claim 1, whereina plurality of the object sensors comprise line scan cameras and theprocessor is further configured and arranged to process images capturedby the line scan cameras to identify an indicium for each object.
 6. Asystem as in claim 5, wherein the indicium comprises a bar code, and theprocessor is configured and arranged to identify the bar code.
 7. Asystem as in claim 6, wherein the bar code further comprises characters,and the processor is further configured and arranged to identify thecharacters of the bar code.
 8. A system as in claim 7, wherein thecharacters of the bar code are identified using an algorithm selectedfrom the group consisting of an optical character recognition algorithmand a matching algorithm that is based on a comparison between charactershape and a library comprising selected possible character shapes.
 9. Amethod of asynchronously identifying an item within a sensing volumecomprises: determining at least one parameter describing objects as theyare relatively moved with respect to the sensing volume, using aplurality of object sensors, each having a known position and attitudewith respect to the sensing volume; producing position informationrelating to the relative movement, wherein the position information doesnot comprise system clock information; and associating the parameterswith respective ones of the objects on the basis of the positioninformation and on the basis of the known position and attitude of theobject sensor that determined each respective parameter, without takinginto account system clock information, and to, for each object having atleast one associated parameter, compare the at least one associatedparameter to known item parameters to assign an item identification tothe object.
 10. A method as in claim 9, further comprising: projectingplanar illumination at an angle to a path of the objects during theirrelative movement in the sensing volume; detecting a reflection of theplanar illumination; and determining, based on the detected reflectionand the angle, a height profile of each object.
 11. (canceled)
 12. Amethod as in claim 9, further comprising: singulating objects based onobject outlines created from a plurality of instantaneous widthsmeasured by the dimensioning sensors.
 13. A method as in claim 9,further comprising: processing images captured by the object sensors toidentify an indicium for each object.
 14. A method as in claim 13,wherein the indicium comprises a bar code and further comprisescharacters, and the processing images further comprises identifying thecharacters of the bar code using an algorithm selected from the groupconsisting of an optical character recognition algorithm and a matchingalgorithm that is based on a comparison between character shape and alibrary comprising selected possible character shapes.